Explicit Forward Web Proxy, forward proxied traffic over IPSEC terminated on F5 to remote device.

The https server is not the one that you have configured with IPSEC tunnel to the f5 device, right it another device?

I have not tried your settup before but if you send traffic to the F5 device to a normal virtual server maybe with a pool member the web server or a forwarding VS that will use the routing table that should point to the route do you see the traffic using the ipsec tunnel? Basically to confirm that not only the tunnel is up but the routing rules for inserting traffic in the tunnel work (having static route for the destination going to the tunnel or traffic selectors https://techdocs.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-tmos-tunnels-ipsec-13-0-0/10.html )? The wildcard SSL and wildcard forwarding IP virtual servers that are connected by http tunnel the to explicit VS I think will select the ipsec tunnel to destination web server if your routing is correct.

Maybe see:

https://community.f5.com/t5/technical-forum/ipsec-between-f5-virtual-server-and-its-pool-member/td-p/234969

If nothing works also have you tried proxy chaining to send the traffic to the IPSEC device ?

https://techdocs.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-implementations-13-1-0/40.html

https://techdocs.f5.com/kb/en-us/products/big-ip_apm/manuals/product/apm-secure-web-gateway-13-1-0/8.html