Key to winning the City of the Deep Ones is to destroy the statues as fast as you can. They spawn more and more monsters, and if they manifest (Cthulhu face appears and everything shakes), the difficulty goes up. Don't let that happen.

I know a guy who was beaten every level in the game on Eldritch Plane without a single crystal upgrade or Epic perk.

Yes..it's one of the maps with a really difficult start because it has high spawnrate during the first min and several shrines appear too...but aftter surviving the first onslaught it's easyer then many other maps.

Regarding to weapons...you can lock weapons with R if you activated it via options, this way you never pick up a unwanted weapon.

Regarding to abilities...after upgrading the number of uses and mayne with some perks they can be very powerefull but with many other things in TeslaVSLovecraft...you have only a limited control over it but thats part of the fun.
The Setup is different every time, you never know what you will get