Looks like you are generally underpowered. Did you try getting some econ up with TEC? It's pretty cheap after all and might give you the edge in production you'd need without a SB.
Yes, I tried getting trade ports early.
But if I do that too early, I can't get a 2nd cap ship that is needed to prevent my enemies from getting more planets (each planet with credit income of 3+!).
Even if I trade-port my only 2 planets (home and a desert), I can't out-econ the 2 unfair Advents. (Each trade port takes 10 mins to break even, not counting the metal/crystal costs. My game ends in 30 mins if I don't get 2 Kols up soon enough.)
If you see my replay, the only way I could win was to split their forces. Bombard their fringe planets every time they start making a modicum of credits from them. I'm too weak to go for resource-deprivation.
Of course, I will be terribly underpowered to handle their fighter/bomber hordes. I used Kol to do that. I just parked my fighters beside my Kol, then flak burst the incoming fighters. (AI fighters tend to go after my fighters).
Making my stand at home planet is no go. First, no trade port chain. Second, constant bombardment of my home planet pushes my credit income down from 10.1 to 3 often.
I played the 3-player map "Balance of Power", in case you wanna try this masochistic experiment yourself.

I took 2.5 hours to beat the 2 unfair Advents.
I'm unwilling to go Entrenchment yet, until the AI is beefed up more and any balance issues ironed out first.
By the way, the Kol's gauss gun is fantastic. Just make sure you fire it at a target with only 15% shield mitigation (and not 65%).