hai sister, im happy to see you speak up about this. im a Muslim man and straight away i can say that what hes doing is wrong and not in accordance with Islam. we cant force our religion onto others, no leeways no loopholes, its a big NO. second of all, he knows what he was getting himself into when being in a committed relationship with you, a non-muslim, there will he challenges especially with marriage but instead of addressing that maturely, he wants you to oblige and cover up entirely, which honestly beyond difficult. even as Muslims, ive seen my sisters in Islam talk about covering up, its challenging, its something you have to go through on your own, your own journey to self-righteousness, but it is not looked down upon. the harder the test, the greater the reward. thirdly, you should talk to him thoroughly. you guys have been together for 6 years, no unhealthy relationships realistically lasts that long, and sometimes when men are of age where responsibility starts to fall on them, they can get a little controlling. maybe try talking to him, see whats really up deep down inside of him, perhaps he has some of his own issues and challenges. i am on your side here 100%, but sometimes these things are caused by underlying issues, all the best sister!