Go ahead and google it:
https://www.google.com/search?q=split+t ... ge+windows
You'll see that almost everything is dated 3-4 years ago and going through the top couple of pages of hits you won't really find any solutions.
Even the Deluge doc page here:
https://dev.deluge-torrent.org/wiki/UserGuide/VPN
states:
Now I don't know when that was last updated, but I don't expect the current state of things is much better.The least traumatic [lazy] way to achieve Split Tunneling is a branded OpenVPN client of a Tier1 paid provider. By my estimates fewer than 10% offer this feature reliably.
I don't doubt that much of what you say in terms of SOCKS5 privacy and possibly functionality is valid (though I do dispute your explanation of seeding over SOCKS5. I have uploaded plenty to private tracker and get peer connections who seed from me. This is without me downloading anything, since I am the originator of the upload), but I do dispute your assertion that setting this up on a Windows box which is also used for other functions (and thus the network connectivity of those other services cannot be compromised) is a trivial thing.
I've asked you, I've asked on reddit, I've asked other places several times over the past few years and as of yet no one has been actually been able to provide a solution.