A few things to clear up - the heater. His room is ok without it, if a little on the cool side, the heater is supposed to be an extra, a top up. DS1 has one as well and very rarely puts it on at all, but DS2 will go upstairs to fetch something, put it on and then come back down for hours, so is heating an empty room. He has not been left in an icebox.
If his bedroom was fine without a heater he wouldn't need one in the first place would he? You're backtracking now because the majority of posters have called you out on the abusive behaviour of your husband towards your son including removing a source of heating in his 'on the cool side' bedroom.
DH is having treatment, both counselling and medication for his stress/depression. He can go for long periods of accepting DS2's behaviour, but then it all gets too much for him and he blows. He doesn't seem to be able to start with a clean slate, and so each little careless thing mounts up cumulatively, with him saying things like 'He (DS2) always..../he never....'
Why does your husband mercilessly pick on your middle son yet has perfectly healthy relationships with your other two? You are using your husbands supposed 'illness' as a get out clause of how you are both shit parents and probably make your middle son feel like utter shit.
I'm not necessarily trying to defend my DH, just explain more clearly, he had a crap family life as a child, so I suspect mega punishments were dished out, and his emotional needs were ignored.
So your husband had a crap family life and he is making his own son feel the same way he did? The fact that you are justifying his behaviour makes you worse than your husband.
I do love all my DS's, DS2 takes up more of my brain space, I worry about him a lot, he seems so unhappy. DS3 probably takes more time as he is 4 so needs more attention. DS1 is 15, fairly self sufficient, providing he has enough food, and has a wider variety of interests and friends.
Of course he is unhappy, are you deliberately being obtuse? Your son is unhappy because of the horrendous family life he has to endure. This lands firmly at your feet and your husbands.
I get that you are going to say DS2 is unhappy because of DH, but I think it is more of a cycle than that, and they are making each other unhappy. Yes I know DH is the adult and is the one who is in a position to make changes.
It's not a 13 years old childs responsibility to make a grown adult happy. Stop laying blame at your sons door. Your husband is a disgrace and I don't know how on earth you can justify his appalling behaviour.
To the posters who say I am a crap mum, well if I was I wouldn't be so worried about this, would I? I know things are far from perfect, and this was a step to making it better. You are entitled to your opinion, but that seems very harsh.
You're a crap mum because you have let this abuse go on for 4 years.
My opinion is that of a mum. I spoke to my husband about this last night something that I would never normally do as I don't pay any particular interest in most threads, however I was actually upset for your son and how he must feel. My husband was flabbergasted at how a father could treat his own son with such contempt.
I don't think either of you are fit to be parents. I may sound over dramatic but I love my children so much and it would kill me if my son felt the way your son feels.