At the risk of repeating questions from a previous post, do you have another known good 800K drive? The answer to your first question is YES! Floppy drives destroy disks all the time. You should definitely confirm a disk in a known good drive before you possibly destroy any more disks. As for question 2, it depends on what, if anything the drive is doing to them. Norton Utilities and others had some pretty good HFS floppy recovery utilities. However, the drive needs to be functioning perfectly before you can use them. If they were 400K disks and they have been damaged, it is almost impossible to recover them as I have yet to find an MFS recovery software that is intuitive enough for me to use. Another possibility is that any number of floppy related chips on the logicboard are bad and are causing the problems. In which case your disks are likely fine. Until you get a KNOWN GOOD drive and system, it would be hard to say exactly where the problem lays without potentially destroying more disks.
Have you posted about your hard drive problem before? Has anyone suggesting the SCHD interleave formatting? The SE uses a 2:1 and the Plus uses a 3:1. All other systems use a 1:1. If your drive is not formatted 2:1 then it would take a lot longer to access the information from the drive than it should.