Faerine

I am currenly working on my F1 OPT, which expires at the end of August. Currently I have an H1 petition pending, which should be approved on time for my H1 status to start as my OPT expires. (Employer is outside of the quota). However, there is a possibility that I may lose my job meanwhile. If that happens, my fiance and I plan to marry so that I move to F2. He is in regular F1 status, not OPT. My question is, in such a case, can the current H1 petition do harm? If I apply to change status from F1 to F2 while I actually have an application to change status from F1 to H1 running, what will happen if the end of August comes and the H1 is approved before the F2 is and I don't have F1 to change from any more? Or can I somehow withdraw the H1 petition?

Also, it is possible that my job does not end until I am way into H1 status. Is it easy to switch to F2 then?

Thanks!