Put the leg back on. No one is even going to notice that.

I routed the particle up about 2" and about 1/2" deep. I cut a piece of plywood with a rabbet cut and glued and screwed it to cabinet. Then I finished it with bondo

Nice work!

Kilz original is pretty smelly.
As far as clearcoating over latex, i have clear coated over createx but not other latex paints.

Does all of this polishing remove the original zinc plating?
Is the metal more susceptible to rust?

I have not tumbled parts but seeing those parts shine made me think the plating was gone.
They do look freaking fabulous though.

I have used a router to remove damaged plywood leaving whatever veneer layers are good. Then i cut a-c or b -c finished plywood to make the thickness i need. It is sold in 2x2 and 2x4 sheets at home crapo.
I have also purchased 1/8 birch plywood from rockler and reskinned by routing the surface 1/8 and glue on birch.
No matter what you do you will be into that cabinet for some time and money. Might be cheaper/ quicker to find a doner cab.