Seeing it from a couple of angles, theres been a bit of disrespect in both directions. It would be a much nicer world if the definitive rule was "if you don't have anything helpful or constructive to say, then don't say anything". So maybe we can all stop with the negativity and draw a line under it.
Ok, so the SLC ain't great at the moment. But you have encapsulated the cables so you not going to have any issues with over heating cables so thats one box you can tick off. The only thing now is that because its a little bit up and down, you've made it a little bit more difficult to tile.
If this was my floor, as it is at the moment, i'd be getting a spirit level over every last bit of the floor. Find the highest point and using a 2 or 3m straight edge, skim/feather extra slc over the whole thing to make flat. Doesn't matter if the floor slopes very slightly, flatness is going to be more important than anything.
Its difficult to get perfect, but the flatter you get it, the more confident you will be that you will be able to get 100% coverage of adhesive without any slumps or dips. At the end of the day, no-one is going to see the slc so don't worry about what it looks like. But the flatness of it will be reflected in your tiling if you don't get it good enough. from a DIY perspective, it has to be right, not perfect.
When it comes to the tiling, spread the floor, skim the back of the tiles, bed the tile, twist it, press it, sit on it if you have to, but get the adhesive ribs collapsed, and the tile level with the last one (no lippage). periodically, lift the tiles as you're laying to make sure you're getting the correct coverage and that no voids are present just in case there are still dips in the slc. The trophy you want at the end will be a tiled floor, nice to look at, but ultimately is practical and won't fail.