Re: the smoke is warm and tasteless?
Try putting the grommet on the vase when you put the pieces together using water as a lubricant. I have a feeling you are doing it backwards, by putting the grommet on the stem first then sliding the hookah stem into the vase, that is why its soo hard to put together. If you are still having problems with it fitting correctly then you may need to use a bit of household cooking oil (any kind) the oil will NOT spoil I can assure you on that do not use any kind of lotion as it can contain chemicals that react in a bad way as you already know.
If you are still having problems with it fitting correctly then you need to contact the supplier you purchased your KM from and fill them in on your situation about it not fitting right and see if they will replace your vase with a proper fitting one.