Not sure what impact your K1 application has on your getting a F1. I would guess you have to show that you have strong ties to your home country and that you have no intent to immigrate. So it will up to how convincing you can be.
Bottom line is this-- are you willing to withdraw the K1 application? If you do, and you don't get F1, then you are getting no where. But if you don't, and you want to apply for F1 with a pending K1, I think your chance of getting F1 approved is very slim.