Ok these tanks and most other BCC work purely on vacuum. Meaning when you breathe in, it creates negative pressure in the tube, causing liquid to flow into the wicks. So for one, if you are flooding you may be drawing too hard. Took me a while to figure out but if i try to rip on a BCC it floods like a maniac, if i barely draw, they dont wick, and dry hits.
As for the ohms increasing, usually when that happened to mine they were dead and done. If i kept trying to use them i would get floods or dry hits galore from just trying to get them to give me a normal vape. These things are so cheap to replace or rebuild to me its not worth the fuss either way
As for the proper voltage for 1.8ohms i get the best vape around 3.4-3.5V. When i go higher it doesnt seem to improve, only burn out my coils faster. Just my experience, maybe my juice and how it likes that heat, idk!