Well, the difference between .025 and .100 second is .075 seconds. The eye blinks at .500 second, so unless you don't blink you will never notice the difference.
I don't know of anyway to partially block a port. The packets either get through or they don't.
Unless you can cut down the traffic, or remove a hop or two between you and the server, you will just have to live with the higher ping.
All I can recommend is the usual windows tweaks to cut down on services, especially network services. And connect directly to the internet, bypassing any router/switch that you may be using.
By the way, the only time I get 25ms ping is, well, NEVER!!!!