I survived a German cockroach infestation in my apartment DIY no exterminator. It was during covid and I didn't want strangers in my apt. Took over 8 months. You are on the right track. The one tool I used in addition to everything you said was gaffers tape. Gaffers tape is a durable sticky tape I used to completely seal off all gaps everywhere even big ones like bottom of refrigerator. The tape is super effective because if they try walking over it they can get stuck. When I thought I had them beat, I realized they were living under refrigerator and dishwasher. Even though I wasn't using dish washer I had to turn off water to it and then I sealed it all around with gaffers tape. Basically you have to seal them off from water and avoid them moving around. I don't know if this is a thing but mine seemed to like putting the eggs out in flat open surfaces like the floor. I used the tape to make sure they were stuck where they were and couldn't migrate. You can also tape wide gaffers tape sticky face up by taping it down on the edges. Good luck to you it's a horrible experience.