I love your tree the way you've styled it.
My experience, window screen and really fine roots don't go together well, as you experienced. The screen is too fine mesh so when the roots grow thru and start to thicken they get stuck hard. Also the fine mesh of a window screen can clog with fines and impact drainage over time. I use plastic screen I buy at Walmart or Michael's (I think it's called crafter's grid or something like that, my Ex used it for cross stitching) that is about the same size as the bonsai screen I used to get online but way cheaper. Hope you find that useful.