[souffle]

It looks like a tumour to me. It is likely coming from the pouch area which is why it is red. I'm so sorry this has happened but I would say this is not operable. Look deep in your heart and decide if his life has become a burden to him. It looks painful and he cannot eat and do normal hamstery things. He is quite an elderly lad now and you have tried your best for him. I think it is time to give him the greatest gift of all which is peaceful rest.
Be strong and remember your decision made from love is the right one.
I hope his path is gentle x