I also think Kelly/David thread makes sense as separate from Kelly/Donna/David thread. They did have a sort of sibling thing going on without Donna, and in S1 she played no role in their complicated interaction
They went through so many transformations, but I still sort of think of David first and foremost as Kelly's S1 stalker. I loved how she gradually accepted him though.
Now, about the question if she had a crush on him... I don't think so. She used him to avoid Steve and to help Brandon's campaign, but that's it. Not just he was dorky, he was younger than her and did not use the best way to approach her
I mean, who would want to date an indiscrete stalker?!
Beside, Kelly was into cool guys. In S1 she tried to make a move on Dylan and Brandon, and her exes Steve and Roger were considered cool... Ross Weber, the guy she lost virginity with, as well. She said in Spring Dance that she dated all the cool guys in school and that she's fed up with them though. So maybe there was a chance for David hadn't they decided to give Donna more space and therefore pair them up. If he had been more of nice appreciative kid maybe Kelly would have decided to go for that instead of coolness and popularity. Kelly and David did share sweet moments in Perfect Mom, B.Y.O.B. and spring Dance. The way S1 looked, I think it sort of headed toward Steve/Kelly/David triangle. S1 was open for so many possibilities