I get frustrated by my hands
You and me both!
There is another thread about this issue of unscrewing mods from attys, they do get stuck often.
I won't post a link to the thread as it goes on a bit, but the summary is this. You can wrap elastic bands around the parts to get a better grip. Better still there are things called Vape Grips which are strips of rubber, you can buy them or any strip of rubber will do such as from a bicycle innertube. You could also try wearing rubber gloves.
This works for me, except on days when my hands are stiff and weak. I have wrapped rubber bands around a special type of pliers called pump grips.
You can buy 'soft jaw pliers', ring pliers, you can also get strap wrenches... all are professional tools, pretty expensive and overkill. But this is a problem that happens so often it is worth spending some money, especially for those of us with weak hands. I haven't had time yet to look into jar openers, bottle openers etc.
As for tanks, the Kayfun v3.1, Kayfun lite, kayfun lite plus, kayfun nano... Clones are cheap, you can get parts for them, even custom parts, most of the parts are interchangeable. Tried and tested kit. I suspect it will be around for a long time to come. There are other tanks which are similar and based on the same sort of idea such as Squape, Fogger, Orchid, ...your mileage may vary, people will have their own favorites.