I’m going to have to second hedgehog’s ideas of cleaning your bed and drying your tpu. Your filament says it should be good for a nozzle temp of 220-240, so I would expect stringing at 235, but it sounds like you are experiencing something a bit more extreme than “some” stringing.

I have no clue about that. I only recently stumbled across the orca setting while waging my own battle against excessively aggressive supports.

In Orca slicer, if you use tree supports and hybrid, an option appears (advanced must be enabled) for something like “Essential supports only”. It is so much better than spending all that time adding or blocking supports.

Print with larger holes, but then use multiple layers. Like Russian nesting dolls, but each “doll” would be rotated very slightly.
Also, try slots in opposite directions. Horizontal slots nested inside vertical slots would effectively create a mesh.
Flat panel inserts could be printed easily and then slid into a circular holder.