It sounds like all that paint has to go. I would use chemical strippers to remove it, like Aircraft Remover. If you hadn't put all that other junk on top of it, this never-curing paint might have come off with plain old paint thinner. Too late now.
Oil base paint is supposed to dry out, obviously... And do so quite definitely, with far better hardness, un-stickiness, and gloss. That's why people use it. It's a slower dry/cure, but not days.
It sounds like this paint is defective, e.g. contaminated, ruined from age or improper storage.
Or, maybe you did not read or follow the instructions - some paints need reduction (thinner), support chemicals, or are even 2-part paints.
That's the thing about paint. It may seem clever to save $30 by using old paint... but when you're wrong, the damage it does to your projects is staggering.
If you have a paint of unknown provenance that you just love, paint a piece of scrap (at least 4 coats so you are getting true color not print-through) and take it to a commercial paint manufacturer. They can mix it in an alkyd enamel, and you'll like the result despite your experience with this defective paint.
As for latex, that's for buildings. It never gets really hard (unsticky), and it can't be overcoated by anything but latex.
How do you dispose of old paint? Paint something you don't want, then throw it away. Any other choice is a tangle of environmental regulations and pitfalls.
One last thing. What were you thinking, putting latex on top of oil paint - least of all, oil paint that had never cured??? It certainly is tempting to try to solve a paint problem by overcoating, because that's easier than stripping. But that Just Can't Work - any layer of paint cannot be stronger than the layers below it. If you were just "trying random stuff hoping to get lucky", you should never do with paint because again, the damage done by a mistake is staggering!
The only way to overcoat dissimilar types of paint is to
- wait until the paint fully cures (and notably your paint was never curing)
- wait an additional year
- scuff-sand thoroughly to create "tooth" for the new primer to bond to, and
- apply a primer appropriate to the new type of paint.
And even then, this is hit-and-miss when overcoating latex. Latex is a jealous partner!