hi,
Once you erase the API code, how will you re-write it with new code, using the API ???

Why I must erase API code? Is RD2 Flash not byte-programmable? I do not see any problem to replace bootloader code which does echo on UART with some NOPs (0x00) without erasure of the entire bootloader/API area.

For "one-handed surgeon" I can give the next solution: put a recompiled copy of temporal bootloader at another address, set boot-vector to it, then restart MCU, erase original bootloader ^*, place modifyed one to there^*, restore factory boot-vector and erase that "temporal" bootloader^*.
^* - is possible with small piece of additional code.

Finally, read messages more careful: I said in previous one:
Indeed, it should be done careful because IAP may corrupt/modify itself.

Regards,
Oleg