@hrx
The problem was solvable after quite a bit of research and testing. Most things stemmed from either the older versions of DCO in previous pfSense Plus version, but a few remained and were able to be debugged to being a problem in the implementation of OpenVPN, DCO and pf in FreeBSD itself. The quintessence is that OpenVPN multihome CAN'T work properly with DCO and PF in FreeBSD right now. Switching that to UDP on localhost and working with inbound redirection rules made it work in no time. It's not as elegant as we need to redirect v6 traffic, too , it's resulting in 2 OpenVPN servers instead of just 1 for my case, but at least it's working that way and doesn't have a problem.
Cheers