@Katharsas Finally got it. After some more playing (and watching your very helpful video) I found out my main problem was running low on power generation so I couldn't upgrade my ACU's gun and get to Tech 2 at the same time. Spamming T1 power generators helped me get over that. Thank you for the video and the tips.
Also found out that the waves are slightly randomized (based on the AI's building, I guess) and I was just getting super unlucky for my first couple of tries.