Use as fat of a first layer as you can. So for 0.2 mm layer height, set the first layer to ~150%, not 90%. This will help buffer any height variation across your substrate.
Include a skirt and/or brim to cover 75% of the support area with a fully solid first layer.
Edit: You could also add a manual block of 0.2 mm (or whatever your first layer is) height selectively in the area you want it to print. Try Tinkercad.com if you don't already know CAD. The supports will generate on top of this block, but there will be a 1 layer gap.
Print the first layer at 220 or 230C, then set layer 2 to your normal 210C.
Increase your pillar support resolution to 2.5 or 3 mm.
If all else fails, try this:
https://www.amazon.com/Platform-Sticker ... 01H35YR7Q/
I print PLA at 35C on this. It sticks amazingly.