Honestly, none of those are good options. You are right to drop #3 - I don't know of any flyertalker who would recommend connecting in PEK. Option #2 is the least bad. Since RDU-EWR-LHR are morning flights they are more likely to be on time. Less than 2 hours connection at LHR is tight, so the extra 20 minutes could mean the difference in catching the SQ flight vs overnighting in LHR.

After you book, keep checking to see if a better routing opens later. Also, with the flight more than 8 months out, there is the possibility of a schedule change which you may be able to use in changing to a better option.