1. $1,000 / month / person sounds sufficient, living with family.
2. I think paying off the loans are good idea, since the loans carry interest.
3. Your username is "trynabootstrap". What would it take to know your product either falls flat or bringing in regular revenue? Do you need to raise money for that? Before you raise money, you will continue to have the option to go back into full time work to "recharge" and work on this part time, and then quit the job a year later and work on it again. Once you've raised money, this option won't be on the table anymore.
4. No, I don't think tapping into 401(k)s and Roth IRAs is a good idea. That's the kind of thing I rely on in case my own money making schemes fail.