Hello!
I want to help you with this task.
I use pfSense and Yealink phones (t20, t21, w52p and some others) and configured OpenVPN on this phones.
So I can help you also.
If you want I can also send you my config file, you just change IP, port, add your certs, key and try yourself... if you want.
About my experience:
I have big experience with network administration (VLAN, SNAT, DNAT, iptables, iproute2, multiWAN, tcpdump...), managed switches, routers...
A lot of experience with OpenVPN servers/clients. TUN\TAP networks, complex routing for separate clients. Serial connection 2,3 servers for more security. OpenVPN over IPv6 and other...
Extensive experience with pfSense routers. I use it in every office in my main job, in my own office, as router on rented servers. What I did with pfSenses: DHCP, DNS, DyDNS, SNAT, DNAT, 1:1 NAT, Destination\Source routing, Carp (2 hardware pfSenses in failover mode), MultiWAN, gateway groups (failover and load balancing), VLANs, a lot of experience with OpenVPN servers\clients on pfSense.
My other skills and reviews you can see in my profile.
Hope for cooperation!
Thank you!