Deleting backups within Time Machine is really buggy, so I just delete them manually. When I ran into this problem (the 2 hours for 1% problem), I found one solution that always works:
1. If trash is open, close it.
2. Hold option and click the trash
3. KEEP HOLDING OPTION
4. Click the Empty button (you shouldn't need to confirm that you want to delete it)
5. Let it run for a few hours.
6. When the progress bar is gone, go back into trash, and empty normally.
And now your files should be gone! Hope this helps 🙂