I haven't watched him a lot (maybe 2 or 3 times) but I will try to answer at your questions.
1. You can judge by yourself by looking at these pictures (taken two days ago, Mahinmi is number 14 with a white jersey) :
http://www.elan-bearnais.fr/cal/0607...07482A%7E1.JPG
http://www.elan-bearnais.fr/cal/0607...074867%7E1.JPG
2. His guaranteed contract will only start when he will sign with Spurs. The meter isn't runing this year.
3. Agressivness, lack of experience (a lot of silly fouls) and poor refs (refs sucks in french league).
4. Euroleague : 12 rbds/40min
French league : 10 rbds/40min
5. I haven't seen him taking 12/15 ft shot. Put backs, transition and basic post moves are how he scored in the games I've watched.