Refinishing Upholstery Leather

[cultureslayer]

I bought a used La-Z-Boy leather sectional that has been mistreated (I've got pets and allergies, no way I'm spending $7k on a new one). As best I can tell, they never trimmed the cats' claws and must have used lysol wipes or something equally terrible on it that dried out the leather on the cushions and made them crack and start to peel off. I realize it will never look new and I should make new covers for all the cushions, but my sewing machine needs a new motor and my bank account needs a break.

I've never refinished leather (just put a finish on new leather) so I have some questions:

Do I use deglazer or would that make the damage worse?

Should I dye it or just use a tinted sealer?

I can't find anything about Fiebing's harness dressing, but if the black version would add a patina or darken the light spots that would be great. If not that, then what else is good for sealing upholstery that will keep it from getting worse? I used resolene on my leashes but I'd prefer the sofa be less shiny.

Should I use leatherique crack filler on the deeper scratches? I haven't seen any other sort of crack filler and I've never used any of their products so I have no idea if it's quality but a few friends really like it for their cars.

Here's photos of the worst of the cracking, peeling, and scratching. https://goo.gl/photos/sQ5owCLEBW7mgc3t7