Seems you have a whole lot going on there and I find it helps to take issues one at a time so to speak. So, starting with your gear.....
I've had my G-Priv kit for over a year and have never had any O-ring issues, still using the same ones I started with. It sounds like it worked well at first for you, before you tried DIY and started doing a lot of fiddling with it. For now, ruling out anything DIY related, get your new O-rings and make sure they are properly installed. Start fresh with a store bought
juice you know and like, and see if you get it working like new. You don't mention at what wattage you used when it was working well or if you have had other instances of accidently increasing wattage. Getting it really hot is the only thing I can think of that would "stretch" the O-rings. I run mine between 54 and 62 watts and find that good for me. Try and get in the habit of locking the touch screen every time when first starting it up. Very simple with a short hold of the little button above the fire bar until the lock appears in upper left of the screen. Once you get that working, you'll have something to hit while playing with your DIY.
Unless somebody has a reason your DIY could cause the problems you describe for your gear, it is a separate issue and you are getting good advice already on that. I would only suggest using something else for testing your mixes and keep what is working for use while doing that testing. Get another
tank (I prefer something small like the Baby Beast) or, better yet, a dripper for trying your mixes. I am not big into building, but my shop sold me a cheaper Freakshow dripper, put a build on it for me, and said they would do builds for me when needed. Works great (especially for tasting) and gave me the opportunity to first try wicking, then try wrapping coils.....something I never thought I could manage.
Once you get that all set, be prepared to buy a few other
tanks for your successful mixes.....you'll want to be able to switch up flavors quickly when desired!
Good luck!