I'm so sorry to hear that your little one didn't make it, but at least he's at peace now, and isn't suffering anymore. I know how much it hurts to lose a pet that you love.
However, in this case, it may have been a blessing that he passed away....he had so many things going on that he must have been in a lot of distress and pain, and may not have ever regained his health. Seizures can sometimes cause a lot of damage that isn't reversible, even with the best of care.
I'm sorry that I wasn't able to be of more help to you, and you have my sincere sympathy on his loss.