I'd definitely get yourself a reputable behaviorist or a very good trainer who knows behavior if you can't turn things around soon.
What I would suggest in the meantime is your taking over the care of your dog, from feeding, to walking, to supplying toys, affection etc....and basically, start teaching him deferential behavoir. (link below)
When he is not already in his crate but might like to go in, stand in front of it and block it for a second while you ask him to sit first. When you block it, don't face him squarely. Turn a little sideways and don't stare into his eyes. You can sit in a chair right next to the crate and have a book to read ready. Then tell him "Okay, in your crate" (or whatever your release word is) and sit there and read your book. As long as he is not too worried about your being there, (you were already there first, after all) toss him a treat, something he WILL like and on a hungry tummy.
It sounds like he may be resource guarding the crate so if you're already there, you "own" the crate and are inviting him in. On the other hand, he may not be resource guarding but afraid of you for some reason and in a crate, there is no chance for escape so he gets more growly. Has the crate been used as punishment? If so, begin only using it with really good associations.
Don't correct him when he growls or acts aggressive because that can further reduce his trust in you and you want him to make positive associations where it has to do with you. Don't put him more on the defensive. And don't get rid of that growl which is a warning, a very important communication that can save you from a bad bite. Respect the growl and work on making him feel okay about the things he's growling about and that then,
will get rid of the growl but because he truly feels secure.
At this stage, if it is bothering him for you to go near the crate when he's already in there, I'd give him a little time to get over that first before pushing the envelope. Or...you can close the door and the only time he can go in there (if I'm getting this right that he likes to go in there) is when you control the door. And your opening the door for him is contingent on his behavior. He must sit/wait first. (or some other skill) Make every lesson fun and rewardinding, cheerful. If he bolts to go in the crate before his release word (make sure you use a release word)...close the door before he can go in or body block him if you think he might get hurt on the crate door. Then ask again for a sit/wait and repeat. Get your release word in in a hurry before he bolts, "okay!" Sit right down on your chair and read your book, tossing a treat in every 10 seconds or so. Do this at the beginning of every little session. Do this several times a day for a very short time....5 minutes or so)
Then move onto another part of the exercise: When you leave for just about 6 or 8 ft for just a few seconds and come back near the crate, toss in the opened door a
very high value piece of meat. And then
when he's finished eating it, walk away. Come back and toss in another good treat, wait for him to eat it and walk away. Do this when he's hungry. After a sufficient number of reps or maybe a few sessions, he should be begging you to come back near the crate. As you walk away, he should be calling to you, "Come back, come back and bring that pot roast with you." If you leave the door open, he'll probably follow you out. But if you want to practice this crate proximatey thing, keep the door closed while you come and go away from the crate.
I recommend your hand feeding him all his meals for a little while and asking for some skills or tricks he's learned fist before getting an installment of food; sit/handful, come/handful, shake hands/handful. Do this for a week or so and do it next to the crate. Move the crate in different locations every meal or so. Then just a few handfuls, then give him his whole bowl as long as he is not resource guarding his food.
If he wants you to open the door so he can go outside for a walk, have him earn that first. Anything he likes and that means from the other people in your family (absolutely a must that there is consistency from all, regardless if he's acting aggressively to them), he must not get without performing something first, at least for lots of things. You don't have to carry it to the extreme I don't think and in fact, sometimes that can cause some undue stress. But for the main things he likes and needs, including a lot of your attention and affection. Make a list. Well here...I'll post a link:
Teaching your aggressive dog deferential behavior Read that through and start implimenting it.
If you see no changes, find yourself a good behaviorist because it's vastly more valuable to have someone see your dog and you interact and watch what exactly is going on. All any of us can do on the Internet is partically guess work because we can't truly evaluate your dog so we're going off of how we perceive your post....which we may be missing something or misinterepting something.
The questions that were asked are good to know. And I totally agree about seeing a vet to make sure there's no thyroid problem or some other thing going on.