Welcome, I can answer a couple of the basic questions not related to model.
There is no minimum weight, the 10% you are reading about only applies to engine swaps, is a assumed *as raced weight* for your purposes, ignore.
Regardless of what kind of fuel system chosen, you may utilize the .5 gallon surge tank, saying that, if budget is a concern, the stock tank is a viable option.
Not incentive, just not agreed upon, for the foreseeable future, please discount whatever thoughts you have on the matter of 2 gal surge.
Getting a little grey, your coupler will get no scrutiny, the size of your p/s cooler may or may not get questioned, this may not be a area you need to enhance, there is no rampant power steering overheating issues that I aware of.
Not 100% sure but it looks like you read that correctly.
There is a spec on this, I believe the seat back has to be no farther then 3in from the bar to forgo a brace. Many ways to skin a cat here, someone will chime in.
The fan will likely be fine where it is, if you feel compelled to make a change it will get little to no notice but you are getting ahead of yourself, one would be surprised at the things that do and don't work out on track, give it a shot before modding.
19 and broke led me/us to ChampCar...
While this may be the cheapest/best bang for the buck, ANY racing is expensive, entry fees, fuel for car/truck/food/hotel etc. Once equipped with a prepped car, new tires, brakes, fuel jugs, pop up pit tent etc, expect your race expenses to be, no less then $2500-3000 per event...
Do you already have transponder/helmet/suit and such?
Transponder, rent one the first race, if you get hooked, go buy a used, old style, non subscription, preferably car powered unit, they are almost as much $$ as new but no reoccurring fees and are holding good resale value.
Suit, used high quality nascar suits are a steal @ race image.com, pay attn to SFI ratings and number of pieces (1,2,3,if you have preference)
Helmet, no real recommendations, Zamp seems to be the cheapest that meets spec. make sure to get one rated SA (nomex liner)
Shoes/gloves, Look around, Speedway.com has a garage sale section!
Attend a race, volunteer with staff, volunteer to help a team (we have mentored a few) stick around for the brief after race awards ceremony, there are typically giveaways, namely a coupon for $100 off a fire system, get the inside scoop!