1) Yes and yes.
2) I assume so. Since I think everyone is human unless your GM has some other races thrown in, you get to pick one of your classes as a favored class, which means it does not count when looking at exp penalties.
3)If the feat says you do nonlethal damage on the attack, you do nonlethal damage. That's mostly because the feat was assuming that you were doing lethal damage on the attack before. Besides, "knockout" seems to scream "subdual nonlethal damage."

how does the whole if you do subdual damage equal to a character's current hp(?) he has to make a fortitude check or goes uncounscious thing work?

is it easier to get someone unconscious this way then bringing their hp all the way down to 0?

and i'm thinking of taking heroic surge at 9th level, which would give me an extra move or attack action 3 times a day at level 9. what exactly does that mean by an extra attack action? is that two attacks with one weapon or all four?

If you do enough nonlethal damage to overcome the person's current hit points, you knock them unconscious. It's really no harder or easier than taking them to 0 normally except that you have greater control over whether they go unconscious or you over-damage them and kill them.

An extra attack action would mean an extra attack with whichever weapon you want to use at its highest BAB.

okay so if im fighting a guy a guy that has 100 hp, and he's down to 70 hp, and then i do 30 points of subdual damage to him, he will become unconscious?

If he's down to 70 hp you have to do 71 nonlethal damage to knock him out.

From the PHB:

...when your nonlethal damage equals your current hit points, you’re staggered, and when it exceeds your current hit points, you fall unconscious.

To further the example: Let's say he has 100 hp max. You deal him 30 damage, taking him down to 70. You then deal him 40 nonlethal damage. He's still up and kicking. You then deal him 31 more points of regular damage. Since the total nonlethal damage (40) exceeds his current hp (100 - 30 - 31 = 39), he is now unconscious.

If you do enough nonlethal damage to overcome the person's current hit points, you knock them unconscious. It's really no harder or easier than taking them to 0 normally except that you have greater control over whether they go unconscious or you over-damage them and kill them.

This is technically incorrect. D20 Modern's subdual mechanic is completely different from D&D 3.5. I suggest you look it up in the combat section of the book, since it's kinda complicated. Pretty much, no, it's not at all easier. Though, in real life, it's way easier to just kill someone than to subdue them in a way that doesn't require an extended hospital visit.

The d20 Modern mechanic uses the massive damage threshold, which is a lot lower than in 3.5. Pretty much, if you deal damage greater than or equal to your target's constitution, he needs to make a fortitude save against DC 15 or go unconscious.

This also means that it's practically impossible to knock out average people without a critical hit, and really tough guys are literally impossible without several instances of the brawl line and a critical.

Which I guess is realistic. Average joes can punch the crap out of each other without causing a knockout. KOs are pretty rare and usually based on luck.

1) NO. Combat Martial Arts and Brawl do not stack. I thought they did, too, until I looked it up in the FAQ and Errata. You can either make a combat martial arts attack and be considered armed, but do only 1d4 damage, or you can make a brawl attack that is considered unarmed but deals 1d6. They cannot be used together.

2) There are no multiclassing penalties in D20 Modern, if that's what you're asking.

3) Yes. If the feat explicitly states that it does nonlethal damage, that's what it does.

so if i attack unarmed with improved brawl for 1d8+str, even though i have the feat combat martial arts, the 1d8+str is still nonlethal damage? i'm not trying to combine the 1d4 with the 1d8, i just want to do 1d8+str of lethal damage.

Yes. If you attack with any of the brawl feats, you deal nonlethal damage and you are considered unarmed, meaning an armed target gets an attack of opportunity when you swing at them. If this is a concern, you can use Combat Martial Arts instead, and deal 1d4 lethal damage and be considered armed. You can't use the two together at all in any way, shape, or form.

well that fucking sucks. is there any way for me to do more lethal unarmed damage? i guess i'm going to have to switch to a light arcaic weapon

Aside from taking levels of the Martial Artist advanced class? No.

Though... why AREN'T you taking levels of martial artist?

I didn't really look into that much. i basically wanted someone with a lot of hp and could do a lot of damage. i did 4 levels of strong hero first, then 4 levels of tough hero. I chose armor light, armor medium, brawl, improved brawl, combat martial arts, exotic weapon prof (ripper) personal firearms, quickdraw, simple weapons prof, two weapon fighting, improved two weapon fighting, and weapon focus (ripper), and melee smash 1, improved melee smash, remain conscious, and robust. next level i'm going to take a level of strong for the higher BAB and take advanced melee smash for +3 to dmg.

the whole unarmed thing wasnt the point of this character, that was just a way for me to try and find a light weapon to use. I want to use 2 rippers (if you are familar with fallout 3, we are playing a d20 fallout universe game) except they cost a lot of money so it might be a while till i get one of those.

so if im going to drop combat martial arts, brawl and improved brawl, and pick up a light weapon to use instead, what should i replace those feats with? of course combat martial arts is a strong hero bonus feat, and brawl and imp brawl are tough hero bonus feats, so it would have to come from there.

I suspect these brawl feats are this way on purpose. Automatic crit with a lethal weapon? Um, how about NO. (Although I suppose it's not too different from sneak attack...but considering how much shit you can pile on with "I just scored a critical hit, let's see what I do..." abilities, it makes sense, from a game balance perspective.

It's like "little dogs are good at tracking, and big dogs are good at fighting." This came up in this community a while ago. You can't have BOTH for the same-price dog; you must pick one or the other. Maybe it's not realistic, but it keeps things varied and balanced.

Nothing to add, just wanted to add thanks for asking these questions. I just picked up d20 Modern myself and was thinking of running something with my group. Looks neat.

What do you think of the Wealth system? Haven't heard about it from someone that actually used it yet.

If you ever buy a car, it will be the only thing you ever buy your entire adventuring career, as I understand it.

Yeah, some of the starting stuff can be pretty awfully expensive, but I think it's a good idea. It abstracts what would otherwise be overwhelming. You can't just use a GP system for modern economics.

As a DM who ran Future, it worked really well. There's a few weird flukes that you might run across, but that'll happen with nearly any system. All in all it worked well. Which also gave rise to a hilarious quote from our games...

*Player 2 rolls wealth check for Player 1's item*
DM: "Wait, why is SHE buying you everything?"
Player 1: "I have a wealth bonus of 0. She's my sugar momma."
DM *Looks at Player 2's character sheet. See's +3 wealth* : "With a wealth bonus like that she's more like a sweet-n-low momma."

That's an interesting side-street...a PC could actually play the Mr. Smith of the group with lots of Charisma and several Windfall-type feats to supply the group with stuff.

Hey, Buick + reinforced grille + Driving skills/feats = decent response to a zombie game! rite? :D