Hi there and welcome.
Couple of things--- first, you posted this on the autism forum. Does your son have autism? What advice I give is very different for a typical three year old (which what you describe is just a three year old that hasn't had clear boundaries set for him) verses a child with autism or another developmental issue. So, please clarify the status of that.
I also want to comment that a child can not ruin a marriage. that is between your husband and you and how you handle stress and it is completely unfair to put that on your three year old. If the foundation is weak, couples have trouble at times of stress and it sounds like you and your husband are vulnerable in that way. NOT a child's fault but that you and husband do not work together through difficult times. Are you two arguing over how to handle things? Anyway, please do not try to blame your child for difficulties in your marriage. Please see those as two separate issues to work on rather than thinking if your child would only act a certain way, things would be fine. Because then it will just be the next major stressor that will pull you two apart unless you address your foundational cracks.
Now, three year olds are not very charming and that is normal. At that age, they test the boundaries. They try to run the show. etc. Mouthing by the way is still very age appropriate for his age and kids often do that for different reasons including exploration which he is starting to get out of for his age but also to self soothe. He should have some items he can mouth if he wants to. Kids that are older have special things you can buy that they can chew on if it is soothing to them so rather than be angry about it, understand that many kids do do this and help him find a way to do it so that he is not putting the remote control in his mouth or something. I had a nephew that mouthed everything until almost 6! He's highly intelligent and was just his natural inclination. My sister had things he could mouth at home. And things he could put in his mouth when out of home rather than his hands or whatever was in his hand. He didn't even seem to be thinking much when mouthing things. And touching everything. Very common for that age. Kids do this to explore. If there are certain off limit things, then either put them away for now as I did (my living room had my pretty things and I just packed them up for a little while to protect them and so I didni't have to worry or be saying no and no and no every two seconds) or do just that, no no no (not yelling but with firmness). I also think kids touch stuff and do things like this when bored. So, take him outside to play, rotate his toys so 'new' things (his old things just put away for a few days) come out ever couple of days, etc.
What form of discipline do you use? As I mentioned, three year olds really do test the boundaries (and prepare yourself, four is like that too . . . it does get better at 5 though). I mean, how do you handle it if he kicks you? I do not spank my kids but am very firm. I would take things they LOVED away. I knew what mattered to them. For my older son, it was his beloved blankie. I'd make it clear that if you do X, you'll lose blankie. And he would lose blankie for just a short time. But if he went ahead and did X, I'd follow through. Oh, how he hated it! My younger son's object that got taken away was his pillow. Or it could be the favorite toy of the day. Or whatever it is that really matters to your son. Take it for a short time after warning if you do X, you lose your toy. Then I just had consequences that followed misbehavior. throw a toy, lose that toy for the day. Scream, cry and whine, I won't talk to you until you use your happy voice. Then I'd ignore them. I'd say I can't understand you when you cry and try to talk so you have to stop crying and use your happy voice. And then on about my business I'd go until they stopped. If I was driving and they screamed, I'd stop the car and sit there silent. For whatever reason, that always worked with my boys. If in the grocery store and they threw a fit, I would leave immediately even if it meant leaving my full grocery cart in aisle 3. Then when they wanted juice later, I'd say "oh, I'm so sorry. we have no juice because you threw a fit at the store. we'll try again tomorrow."
I would give choices when you can. Lots of choices. You control the choices, so they aren't really getting their way. But some kids comply much better if they feel they had a bit of control over things through making a choice.
Many parents have good luck with the time out method.
So what is the method you use to help guide him. And that really is what discipline is in my opinion. A way of teaching them. Set your boundaries and lovingly yet firmly hold him to it.
but know, you describe some typical behavior for a child that just needs boundaries set for him at three. good luck