Straightgrain

Hello...been a few months since I've posted.

I'm planning a radiant heating mat system and ceramic/porcelain tile over my existing uneven slab in the bathroom. It is uneven because when the new drains were put (after the original slab was poured), the concrete guys repoured the channels where they laid the drain pipe a little to high (about 1/4-1/2 inch). My bathroom is about 7x10 (not counting the shower stall.

I plan to use Self Leveling compound (Laticrete) to level the floor. Then put down the radiant heating mats (Easy Heat brand).

Few questions if anyone can help me:

1) The floor has saw kerfs where they sawed the channels. What is best to fill those?

2) People have mentioned expansion joints around the perimeter and around toilet drain, shower stall etc. What do you use for expansion joints?? Also what is best to use at the door opening as a boundary?

3) Has anyone heard of problems resulting from putting radiant heat over a fairly new SLC overlay?

4) Finally, my steps would be: SLC overlay pour, radiant heat, thinset, tile. Is that the best order? Others have mentioned put the radiant heat mats on the existing slab then pour the SLC over that, then thinset and tile?

Any other suggestions on steps, procedures, etc would be great!!