This sealer you use, also say primer function?
If the sealer also does primer already then you can just put top coat over it.
If the sealer never say primer, then just slap on matex or maxilite (personally prefer matex or KCC coverage) cheapo white paint then only do topcoat.

Uh since theres some leaks, wet area and oily area..
The kitchen one..maybe consider using gloss paint if very oily and unvented
Also if there is joss stick burning this also cause paint to deteriorate.
As for the bathroom.. make sure grout line in the tiles are good else it will still seep water. If the bathroom unventilated, try to put in a ventilation fan. Also consider outdoor paint if its unventilated and smells damp.