If you have tried the pinning instructed and not helping, then seemingly you'll have to apt-mark hold every single package you installed previously i.e all the deluge deps too, or atleast im guessing as not really into apt internals. Again, I don't know anything about this, and don't have time troubleshooting this now, so don't know mind you.
It might be possible, sure, but this is not really have this works. The author has choosen this way and contributed his work, and if in disagreance about design-choices then of-course is free to make feature-requests, or fork it and add your own spin to it
Cas, lead-dev has been asked about this before and answered like I posted previously.
Last, you could also make a venv of deluge1 if wanted, as I described here for my distro, and another user posted adjusted ubuntu instructions I.e package-names there etc, though I'd guess much easier for you to just apt-mark hold all the relevant packages, if that works, but up to you: viewtopic.php?t=55488