Dear Thea,
I think you've answered your own question. Let's make a list of all the warning signs in your letter.
a) You found out things about him that scares you, but you're afraid to leave him because of your past.
b) He is possessive and wants you all to yourself. This is a big red light. Why is he keeping you away from your friends and family? Probably so that he can manipulate you better.
c) He doesn't allow you to be yourself (makes comments about everything you say)
d) He is jealous. Do you give him reason to feel jealous? I don't think so. This is the typical behaviour of an abusive man.
e) He is chauvinistic and thus doesn't respect your value as a human being.
f) He makes you feel like he's doing you a favour by being with you because you are overweight.
g) He makes you feel that you're "not pleasant to look at."
h) He doesn't support you in your struggle to get healthy and he "keeps you down".
And finally... He threatened you with violence if you ever decide to leave him! And gave you that whole spiel about if he can't have you no-one can.
I hope you can see that this man is dangerous, and bad for you. Please get out of this relationship. You owe it to yourself. Contact a psychologist or your nearest FAMSA branch for advice on how to leave.
Good luck.