Dear OP, as the partner of someone with Obstructive Sleep Apnoea (OSA) which is successfully treated with nightly CPAP machine, I can tell you that his tiredness and habits are classic symptoms. It is a medically urgent matter, I cannot stress this enough.
OSA is aggravated by obesity but obesity is not the sole cause of OSA. OSA can affect anyone - my OH's specialist mentioned treating children, skinny people, old people, in fact people of all shapes, ages, sizes. One risk factor in developing OSA is having a short neck, regardless of body size.
I would suggest that the actual cause of your husband's issues (and hence your problems with him) is OSA with or without obesity! And when he gets successfully treated, you will find he is a 'new man'! My OH certainly was.
He needs to see a GP ASAP, and be referred to a sleep clinic, where he can have a take-home monitor or a one-night monitoring in a local hospital. Insist on him going - it is literally a life-or-death matter as OSA is a killer - and not just from people falling asleep at the wheel of vehicle - it can directly (over a period of time undiagnosed) cause heart attacks, strokes and other vascular issues.
There are many makes and models of CPAPs and several ways of wearing the facial 'mask' bit, it's important to try them out and find one that works.