Can pretty much seed anything right now with clover. It's so moist & cool u will get away with a lot. Won't get some benefits of rye but do keep it mowed as time goes on. Thistles- can keep em aggressively mowed. U have a lot of options though. I'd read the BUTYRAC or 2,4-D,B label to see if it covers thistles. Not sure on that one. Another option is hitting with glyphosate at a higher rate and inter seeding some more clover. U likely would not kill the clover even with a quart per acre. Even 2 usually doesn't do it but it will be a hard hit to clover so may leave as second to last resort. Last resort is frying the whole thing and redoing. Another spray that could work on thistles (read label, not sure but I think I recall it working on thistles at certain stages) is PURSUIT herbicide. Probably be my go to if mowing didn't work. Expensive but low rate usage so it's really not expensive. Much cheaper than redoing plot. Lot of options.