Similar issues.
PP EDLs are junk. One thing to look at is the REEL ID. PP put the file name as REED ID and this has thrown off Resolve for the last two jobs I have done on PP. We fixed this by going to the list and deleting the .R3D extension and leaving only the 16 digits RED gives the files as a REEL ID. This allowed RESOLVED to see it.
We are cutting :30 so our lists are not deep. If you have a big show then that work may be tedious.
Also we saw discrepancies in our source TC version the TC on the list. 1 frame off here 2 frames there. Again junky.
have not tried the round trip to FCP. Might try that.
good luck