Fight Dirty?

[Aloofi]

If you are playing unmodded use fighters. I've never played PBW, but unmodded fighters are really, really mean.
Six carriers with a full complement of fighters should send his fleet to the bottom of the galactic sea.
Don't forget to include in your fleet enough minesweepers to clear the way ahead of you.

Also, don't waste more money in satellites, fighters are more cost efficient for warp point defense. Research fighters all the way up and cloaking, so you get some stealth carriers into his territory.

Still, sooner or later he is going to get his main fleet together and drop it on you. When that happens make sure you don't let your ships be taken one by one. Park your fleet on the most valuable planet on the system the battle happens so you can bring your weapons platform to bear, add some mines on top of your fleet if possible, transport all weapons platform, troops and fighters avaliable on the system to this planet, and don't lose your patience when he glass the other colonies. If he is a newbie he will fall for it. He will not dare to leave your fleet behind unblooded.