1) i'm interested in making soap both for my hospital (as i enjoy an army based defense over a trap based one, so i'll need a hosptial, plus i'm going to start working with magma pistons, the FUN that will cause >_>). I've heard Lye can become bugged and made with a bucket containing water. How do i avoid this?
You can't, really, since buckets with water in them don't get taken to furniture stockpiles (so you can't keep them away from the asheries). You could remove the Give Water task on all dwarves but a dedicated few, since attempts to give water to thirsty working dwarves are the cause of scattered water buckets. If you do end up with a lye/water bucket, there are a couple of fiddly ways to do it in-game. The first is to haul the bucket but not the water to the trade depot, and the second is to have the bucket used for milking. This will remove both the lye and the water and replace it with milk, and the bucket will be returned into circulation once the milk is processed into cheese. The DFhack suite has a function for removing water from buckets, which is a much less stressful solution.
2) in a 200 population fortress, how many should be soldiers to actively deal with level 3 caverns, late game sieges and mega beasts.
Twelve. And a half. Got to have your mascots!
Seriously though, it depends on what you want to do. I have 24 soldiers on a 4x3 with about three squares of edge sealed off with bridges*, and with 16 of them on the job it's just about possible to have the edge constantly covered at caravan time. They train in the fortress's only entrance, and because of the way it's set up the same 6 dwarves handle ambushes. The caverns are sealed off, but if I wanted them dealt with I'd set up a second entrance and ensure that it was the only subterranean access to the fortress. For any individual threat two or three sufficiently-skilled dwarves is enough -- a large enemy can use one dwarf as a football, but can't keep two down.
*I found that any wildlife between the wall and the edge would get slaughtered horribly by the border patrol, and I wanted to keep things alive for future use. Eventually it turned out not to be a problem because I have a bunch of wild tigers blocking anything else from coming onto the map.
3) How do i order specific items of clothing to be dyed, and then specific dwarves in the military to wear them?
You need to get a dwarf, the items, and the dye all together in one room in which the dwarf has no access to any other materials. To get the specific items there, you can either use a stockpile to pull them from wherever they are, or set up a dump zone and dump the individual items. Once the items are dyed, you can go into the View / Customise screen and use A, L, H, etc. to get to the 'specific armour' option. Then you select the item off the list, being careful to assign only items that have yet to be assigned. You'll have to keep track of the list yourself, as already-assigned items are not removed or marked.
4) How much use is the textiles industry in general? I've never relied on it before, my wealth usually comes from gold / rock crafts
It's kind of a luxury industry, and it's a great way of occupying terminal malingerers. Cloth is one of the few raw materials that can have a quality level, and dye can be applied to it to make it even more valuble. Once you've made something with that expensive cloth, you can apply more expensive cloth to it in the form of cloth images, and multiple images can be sewn onto something.
5) What's the easiest way to attract a dragon to my fort? (i want to tame it, edit the raws so it isnt EXOTIC)
Once you start getting megabeasts, all you can do is wait for a dragon to show up. You could also embark on a cave containing a dragon, but this is risky and cuts down on your potential embark sites quite a bit.
6) For a very interesting game, what should my world gen settings be, and what kind of area should i embark to? (Not a really hard one, but an intermediate kind of area)
Turn minimum savagery up a bit (20 should be fine) and increase the amount of evil regions considerably. A tenfold increase is a good start. That's a quick and dirty way of getting more Terrifying areas, although some are more terrifying than others. Ogres are pretty scary, and live in shrubland / savanna / grassland. If you want to tweak savagery some more, you can use the weighting options to encourage the game to create islands of low savagery that will allow for civilisations to establish. After that it's up to you. Most biomes will be adequately represented in the average map, although the default temperature settings tend not to create large areas of glacier or tropical biomes. There's also rather a lot of ocean taking up the average map. If you do start doing a lot of fiddling, remove the 'minimum number of <whatever> squares' requirements, otherwise you'll get infinite rejections with some settings
7) finally - how do i get captured animals to fight each other? i want to make an arena, and getting a tamed bear i bought off the elves to fight one of my dwarves (unarmed like a boss) didn't work
Once animals are tame, they're completely unaggressive unless cramped. To get a tame animal fighting a dwarf, you need to force them both onto the same tile. I think you could do this with a 1x1 room with a lever in it which operates the door. Door is open, dwarf goes in and pulls the lever that seals the door, bear is manually dropped in from above. Don't forget to make the door operable from the outside, you don't know who's going to win.
EDIT: Bonus question - How much does designating high traffic, low traffic areas increase fps? is it worth it? (i've already set G_FPS and such things to help, i can hold steady on 40 on my 10 year fort during a siege)
Not sure about FPS necessarily, but it does make things more efficient in high-traffic areas. A high-traffic stripe down the centre of a 3-wide corridor being rushed by 60 hauling dwarves results in a tight double conga line with lots of dwarves dodging into the outer tiles and a few getting knocked over. The same corridor with no traffic designations has a lot more shoving and tripping going on.
It depends on your fortress layout too. Wide open spaces and other deviations from the eventual path are the things that really hurt the pathing algorithm, so the less sprawl you start with the less direct FPS gain you'll see.