Need advice...pet and dog lovers only. my cairn/silky terrier is 8 years old. he has epilepsy for 4 years, he?

was recently diagnosed w/diabetes, then cataracts and now lipids in his eyes, which prevent him from getting catarct surgery. he is on a special diet of real chicken and rice only. he gets pills 2x daly n liquids 1x daly for the epilepsy. i have to inject him 2x daly with insulin. he's on 3 different eye drops 2-3 each, daly. to add to this, my husband has a 14yr old beagle who is very territorial. (when my dog wanders around aimlessly b/c he can't see, he bumps into the beagle and the beagle attacks. up until the diabetes n blindness we were managing and my dog didn't seem so bad off. but now, i wonder if he's suffering. he's bumping into walls & banging into things. it's so painful to see. i can imagine how it's hurting him. i love him sooooo much. i also have a new baby in the house which also requires my time. plus, the financial aspect is draining us. do u think he's suffering? am i being selfish to keep him alive? serious replies only. we don't know what to do.