What the valency of lithium? What's the valency (or the net charge) on the sulfate radical (you can deduce this from H2SO4)? Use these to determine the incorrect formula among the two you've written.
uhh by valency do U mean valnce electrons, and therefore combining capacity? I don't know what you are talking about for the 2nd half of your explanation because I am in grade 12 and we have not done anything like that.
Ka2 for sulfuric acid is not small. I'm most people would call it diprotic.
But saying LiHSO4 is the dominant product is not a wrong answer. On the other hand, LiSO4 is an incorrect formula. The product of the neutralization of LiHSO4 would be Li2SO4.