Sounds all good.
So long as the AutoScript folder is at the root of that flash drive (not contained by any other folder), it doesn't matter if you have other folders on that same drive.
Makes no difference at all so long as they are on the same subnet, you can use a combination of Ethernet and WiFi without it causing any problem.
Definite issue and one that must be overcome before proceeding at all any further with any other troubleshooting. If you are sure that particular USB flash drive was at one time working and no one messed up the script on it, then it should still work just like it ever did. But failure of the drawer to open automatically is symptomatic of the script not being read. I am going to guess that you might have either the Auto-play, or the Auto-resume setting (or both) enabled on the Oppo, both of those settings need to be defeated for this to work.
Either USB port will work, and you do not need to reformat the USB flash drive. An Oppo player can use FAT32, NTFS, or exFAT formatting, so long as the partition scheme is Master Boot Record. Leave all of that alone if you are sure that particular flash drive was at one time known working. Just disable the Auto-play and Auto-resume settings on the Oppo and you will likely be good to go.
EDIT: I see you've got it going now.