I need help, fast. Im tired of the same old argument, Please. (longish)?

So, I;ve been friends with my boyfriend for years, we started dating 11 months ago, and my mom has never liked him. But we went through a rough patch broke up for two days, but then were back together. She doesnt know yet, and I keep trying to tell her but she never gives me the time of day. But because I sleep in, She thinks I sneak out as soon as she goes to bed to see him, but i don't and even if i did? She has absolutely no proof. Also, his parents wont allow him to get his license quite yet. But now heres the problem, He's 18 and I'm 16, so he could get in alot of trouble, but we are very very careful, as in theres pretty much absolutely no touching, so he won't be permanetly labeled as a sex offender and what not. But my mom snuck my phone, and went through my messages. The only thing in there is him waking me up with a phone call like he does every morning, and reminding me to eat throughout the day because he actually pays attention to my eating disorder. So now, she is completely freaking out, and shes threatening to call the police about him, when he has done absolutely nothing wrong. He has the same family problems that I do, so he can get a little emotional, but he never harms me, he never does, he doesn't even yell at me, ever. We have fought only those few times when we broke up for two days, and he has also given me a promise ring. He wasn't able to graduate with the rest of his class this year, because he was going back and forth from illinois and michigan, so he had to make up credits, but hes doing that through online school, while working, helping his mom pay off the house, and trying to find an apartment. But my mum doesn't accept like him simply because she scares him, and will hardly hold a conversation with him, then yells that he won't talk to her, and she notices him avoiding her, but he doesn't he is extremely respectful, and the rest of my family loves him. What can he do, or say, to make her at least accept him? I'm tired of everyday being a war, and no leaving him is not an option, im not just a stupid yound girl, Im a lot more mature then most kids my age, because I've pretty much raised my little sisters, and have taken care of my 19 year old sister most of my life as well, because she can't keep herself out of trouble. So please, don't say I should just leave him because hes too old, because honestly, most married couples I know have an at least 4 year age difference, my mom and step father? Theres a 6 year age difference. If I thought I was the slightest bit too immature for a realtionship with him, I wouldnt have been in it for almost a year now, would I of? So please, serious answers. Please. Any advice that would help a litttle, I would be extremely grateful for.