Do you have symmetric 100Mbps at your home? Most US internet connections are asymmetric, and offer much lower transmit than receive speeds. Try running a speed benchmark (speedtest.net) behind your home router to check what speed you are actually able to transmit.
I am having a really similar issue, if we can solve it, a beer is all yours.
Any help or ideas would be appreciated...
Do you think this applies??
http://winaero.com/blog/speed-up-openvpn-and-get-faster-speed-over-its-channel/
Thanks again.