OK, is it worth pursuing, depends how much your DH earned, and how you can go about fighting this.
Ifthis was an unfair dismissal which it sounds like you could get up to approx £65 k if your DH has those losses. If he gets another job tomorrow paying the same he'd get nothing as he'd have no losses. Also if the company can show he would have been dismissed in say 3 months anyway even if he was unemployed for 6 months he'd only get 3 months money.
The notice moneys would be on top of that and this sounds like a strong claim so that's another 2 months money.
Then there's the DDA claim, again that's based on losses but there's no limit as to how much he can claim.
If he earned say £100,000 pa and didn't get another job for a year that would help as it could get you over the £65k ish mark, but assuming he didn't he can't get the same losses twice. He can however get injury to feelings for discrimination and that is worht at least £5-6k on the usual scale given he lost his job.
If you are paying for your own legal advice assume somewhere between £150 - £400 per hour. Sometimes this will be paid for by insurance if you have it (check your mortgage, car etc). Even if you win you almost never get your costs back. So bear that in mind. Its often worth thinking about the CAB etc as legal costs are a lot! Also on a DDA case there may be medical evidence which you'd need to get and that will take time and make the hearing longer unless the company just accept the depression is a disability and everything your DH says about it (companies rarely do that).
Most cases do settle though and often the comapnies pay soemthing for legal advice to get a compromise agreement in place.
At this stage I would say appeal, and try to get some rl advice from someone as your DH probably has a good case at least from what you've said here. He should however also start looking for another job as its very rare for comapnies to change their mind on appeals, they are mainly going through the motions.
I'm afarid I don't know anything about benefits.
good luck.