Routing and RAS for HTTP(S) traffic

I've different VMs on a Windows Server 2012 R2 host. The VMs are in a internal subnet. I want to forward traffic to a specific VM by port. For example port 80 goes to 192.168.0.2 and port 443 goes to 192.168.0.3. The reason for this is that we've a linux VM with a caching-server. So port 80 goes to the caching-server which try to get the request from cache. If that's not possible, he fetch the request from the IIS backend on 192.168.0.3. SSL cannot be cached by our caching server and is only used for loggedin-users where caching makes no sense, so we want to forward this directly to the IIS backend.

I tried out Routing and RAS which do exactly what I want. But the problem is: Its VERY slow. My test page took about 10 seconds to load instead 1,5-2s normally. I guess the reason for this is that because of Routing and RAS every single request will be handled by a single HTTP-Connection instead using keep-alive.

So I've two questions:

1. Is it possible to use Routing and RAS for HTTP-Traffic and so I'm only doing something wrong?
2. What can I alternative use for this? The perfect solution would be the possibility to forward single ports like Routing and RAS do. The only alternatives i found are reverse proxys like squid, but they do not work directly unter windows