1) For regular play, I wouldn't want to spend more than $25, as opposed to $35. It may not seem like a huge difference, but here in Ontario there's places that are $35, and places that are $20. I have no problem going out every weekend and spending $20 on airsoft, but would not go out and spend $35 every two weeks. Human psychology's fun, eh?
I enjoy playing often, and would much rather spend $20 (for perhaps a shorter time), over $30.
Case in point, there's a field in here in Ontario that will charge ~$35 for a full day on the weekend (over 12 hours), and at other times $20 for ~4 hours. I would rather pay $20 for 4 hours. I may not be the majority, but I know there's a lot of people who feel the same way. ie "I'd like to get out more, even just for a few hours, but it's so expensive".
2) Hell yeah I would! Depends on how often, but I wouldn't want to drive more than an hour on a week day.
3) I wouldn't mind mixing calibres. Just remember how much more energy a reball has, and take that into account with your NVG.
You should also keep in mind, before you blow a ton of money on cheap NVGs, that cheap NVGs can take away some of the fun, once the novelty wears off. It's like playing a laggy video game with nice graphics. Yes it's novel and cool, but if you can't function with them, a player is likely to just opt to using a tac light the next time.