-How long can we reasonably sustain this plan at our current income?
-Is it worth it to move to a place $250+ more for rent to cut out my commute?
-Bf's car has a very worn transmission. My car always seems to have one problem or another. We've discussed selling one car, but he is resistant to it. Would it be better to sell both and get one car that is possibly more reliable?
-What ways could his writing and filming skills make us a little extra money before his career takes off?
-Is it too soon to ask for a raise at my work. If not how do I do it, and how much should I ask for? (1st big job in my career)
- Sustainability: This depends entirely on your and your boyfriend's temperament and patience. You are living below your means and can save a couple hundred dollars a month (if you truly have zero extras - that might get wiped out often with little purchases that add up). Theoretically, you could keep doing that forever, but you'd also have to work almost forever, too.
I think I'd be willing to do something like this for a significant other I really loved for about a year, MAYBE two if I really truly believed he would ultimately be successful with is dream. (I'd do the shorter time period if I wasn't really sure it would work out but I wanted to be supportive). Additionally, I wouldn't be comfortable doing it for anything less than a Life Partner - spouse, fiance, etc. Your relationship may vary.
- Move: I know everybody here loves the live-close-to-work mentality (for me, it's practically a requirement, and I've been known to pay 2x the rent for a walkable commute). But numbers-wise, in your scenario, I'm not seeing how that helps you out. Unless you could go down to zero cars in a closer apartment, so you don't have a car payment, car insurance OR gas ($280), you're not saving enough on your commute to make it worth it, IMO. (Plus, remember moving itself can be expensive. Security deposits, rental application fees, unpredictable new utility costs, etc.).
- Extra money: I'm not sure how to make extra money at attempting to be a YouTube sensation, but I kind of doubt that this new adventure will take up 100% of his time. Could he get a part-time (maybe very part-time) job in the weekends/evenings to help relieve things a bit? Even a minimum wage job, like delivering pizzas, would really relieve the pressure on your tight budget. If he's not even willing to consider such a thing, I would see it as a relationship red flag.
- Car: is he going to be working on his new career from home for the foreseeable future? Are you in a somewhat dense community, where he can walk or a ride a bike during the day if he needs to go to the grocery store or something? If so, I'd say yes, go down to one car. I wouldn't get a newer one if the ones you have now are reliable enough to get by. I'd keep the one with lower maintenance costs or better fuel milage.
- Raise: as a general rule of thumb, 6 months is too early. One year is much more likely to go over well. As a general plug, I LOVE the askamanager blog for all these workplace questions. She has tons of posts about how to best ask for a raise, and when. The blog in general is a godsend for people starting out in their careers. Start with this post and accompanying article:
http://www.askamanager.org/2015/01/want-a-raise-heres-how-to-get-one.html.
Good luck!