What he is offering you is good. You really won't find a dentist in private practice offering you health insurance (it's rare). If you work for a big corporation like Monarch, Western Dental, etc. you'll get insurance.
Anyway, I would just accept this first job with a grain of salt. It's very rare a new dentist will stay with their first job long term. Don't worry about the insurance issue.
I've been an associate for a few years now and my friends and I have been through several jobs. You first said that you have to pay for all lab bills and then later said you won't? I'm confused. If you do have to pay for lab bills, they can add up and take a bit off your paycheck. Every office I've worked in, I've had to pay a percentage of the lab fees (usually 20-30%) which isn't too bad. But if you're paying 100%, that's a lot considering you're only making a percentage of what you produce.
Having a base for 6 months is great! Just learn what you can and enjoy having the freedom outside of dental school! Good luck!