Hello guys, appreciate if you could provide your two cents.

I am considering to use Nippon EasyWash series for painting my whole unit of 1,313 SQFT. Painting area including wall, ceiling and plaster ceiling. Below attachment is the layout of my unit.

1. What is the estimation of paint I need to buy in terms of liter if only to focus on 1 color and assuming to do 2-coats application? I have tried the Nippon's paint calculator and got result of 50L. It seems like too less.

2. What is the purpose of sealer/ primer? It use before/ after the paint? Is it a must to use a sealer/ primer? If yes, how many liter should I purchase? This is because Nippon website suggest to have 1 coat of sealer/ primer together with 2 coats of painting.

3. I was quoted for RM 4,500 to paint the whole unit and the supplier doesn't mention the specifications so I post this to ask about the market rate, would it be cheaper if I DIY myself in this case?

Can you guys see the post?