Something else you really need to consider is where you really intend to raise your child. It won't be long before he is in full time school and this will tie you down. It isn't realistic to think that you can just pull him up out of school and haul him across the continents if you change your mind or things don't work out. Once maybe, but ultimately, at some point, for the child's sake, you'll need to decide where you want to be and stay put either in one place or the other.
The "process" to gaining your permanent residency in the UK is not automatic by any means. It isn't cheap either. You have to be serious and committed and decide that this is what you want to do.
You also have to decide if what little you have invested into your marriage at this point, and also, what little your husband has invested into the child as a father, is worth nurturing, developing and holding on to for the "forever". The child is at an age now where memories are forming and character is developing. If you think at all that there's a chance you cannot be happy here and will ultimately be happier at home in the States amongst the support of extended family and friends, NOW is the time to make that decision. I think the longer you wait, the more difficult it will be for your child, especially once he has established a bond here with the father.
Then you should ask yourself also, if you do decide to stay and become resident here, can you be sure that your husband (who is not even a UK citizen?) will not want to later pick up and move back to Romania or elsewhere? And then where would this leave you and your child?
You seem like a sweetheart and to me it seems like you're in a difficult place with some very hard decisions to make. Nobody can tell you what to do. However, if this were me, I think I would cut my losses, pursue an amicable separation and take my kid back home and raise him in a familiar environment with the support of immediate family and whoever else you have around you. I take it you were married in the States? Had this child in the States? You were trying to do the right thing at the time but globe trotting isn't part of the deal unless you want it to be.
Do you have parents that you get along with at home in the States? If so, I would let them speak and consider their feelings in all of this too.