Submitting a I-140 shows immigrant intent since its self-petitioned. If it was employer petitioned, it would be a little weaker but this is a clear case. You don't qualify for F1. Plus, you can't transfer from J1 to F1 anyway, you need a visa stamp (specific J1 restriction). You will definitively not get a F1 visa stamp outside the US, and you won't be allowed to reenter. Make sure you talk to an immigration lawyer before filing any documents or leaving the US.