[Taera]

Im not an expert and have little experience in PBW but...

scanners are annoying and if he is the way you describe him he prolly has none.
Remember that Stealth armor gives you cloaking.
Dont send in a fleet - send in hunter ships that would pick on colonies and lone ships. Find his central production sites and plague them (not useful this time tho as it seems). Also find his mining colonies and rad-bomb them. If you need to take on a planet remember to bring in some planetary napalms, they're quite useful.

Vary your tactic - once try on with a lot of fighters and missile cruisers, then when he gets PDC go in with some direct-fire weapons.

For warp-point combat consider the Graviton Hellbore weapon. though many might jump on me here nothing compares with it in a single-shot.
Either that, or ripper beams.
SHield depleters, dont forget these.
And hopefully you do have ID's.

Part of fighting dirty is exploting those special weapons. Some are economically taxing though.

You're psychic? Why arent you using your psychic weapons then? they're some of the best in the game. having cruisers armed with psychic weapons can bring you a couple of victories.