If you're getting 1.5Ω from an 8-wrap coil of 28AWG (0.32mm) wire with a 2mm inner diameter, there's either something wrong with your wire, something wrong with your ohmmeter or something wrong with the way you measure 2mm. I use 8 wraps of 28AWG on 2.5mm out of long habit (it was a great fit for a generation-3 Kayfun, likw the KFL, KFL+, 3.1, etc.), and that comes out to 1.4Ω using Kanthal A1. It also happens to be a good fit for a Dvarw, using the 0.8mm insert at 8.5-10W (depending on the e-liquid flavour) and 50/50 (since I DIY, I don't rely on what the bottle says the ratio is). No leakage, no seepage. And yes, I chain - I vape a little heavier than I smoked, and I was at two packs a day at the end. You can't blame this on everyone else being all "clouds, bruh" and using huge coils.

Yes, the tank can tolerate a smaller coil, especially with the smaller inserts, but I can see how the oval holes might be a problem if you're not using enough cotton in a smaller coil. You don't have to stuff it or anything, but you do need to make sure that the holes are covered - if you can see the deck from the outside, so can the juice. With a small coil, it's probably easier to leave the tails a little bit long and have them hit the holes horizontally (as in Gatok's photo). But it ain't the tank that's the problem.