Help with complicated VPN channel

Infrastructure: VM with MS TMG 2010 Server (Win2008 R2), connected via virtual adapter to VM with SoftEther VPN Server (CentOS), which is connected via TAP adapter to remote VM with OpenVPN server. Situation: I can VPN from all of my internal networks to SoftEther and work through remote OpenVPN server. Now I want to VPN to my SoftEther server from Internet. Troubles: I can not make port forwarding for L2TP work on TMG, which is PPTP VPN server itself (may be this is the trouble?). I can not even make SoftEther client connect via 443 port through TMG, and I do not understand, why. Task: find the way and help me to configure the system for I can VPN to my SoftEther Server to browse Internet through remote OpenVPN Server. P.S.: I even tried to change TMG to Mikrotik CHR. No result.