I'm booking 2 tix RDU-SIN in early December using United miles and am presented with 3 choices for the outbound leg, all of which have tight connections that make me nervous. I wanted to get advice on which seems most doable:

DOOR #1 :
RDU-IAD 605a-718a, 1h17m connection
IAD-LHR 835a-850p, 1h15 connection
LHR-SIN 1005p-700p (first two on UA, last on Singapore)

DOOR #2 :
RDU-EWR 600a-736a, 54m connection
EWR-LHR 830a-830p, 1h35m connection
LHR-SIN 1005p-700p (first two on UA, last on Singapore)

DOOR #3 :
RDU-IAD 1021a-1134a, 1h1m connection
IAD-PEK 1235p-340p, 1h connection
PEK-SIN 440p-1120p (first two on UA, last on Singapore)

There are other flight options with safer connections, but they all arrive in SIN in the early early morning, and if possible I'd much rather arrive at night so we can go to straight to bed and sleep rather than attempt to stay awake all day with no hotel room available till 3pm-ish.

My first inclination is to ditch Door #3 because I have never heard ANYONE say anything good about connecting through PEK, especially with only 1 hour. Door #3 also puts us on United metal for the long segment, which seems less desirable than SQ metal (we'll be in Economy, which I find bearable on SQ's A380 but I don't know about UA economy for that long, even in the Dreamliner, because I'm 6'4".)

Doors #1 and 2 both seem dangerous because of the tight connections. I would probably lean towards a 1h1 min connection in IAD over a 54 min cnx in EWR, but the IAD route then cuts our connection at Heathrow to 1h15 min and we'd be trying to make the last LHR-SIN flight of the night, which means if we miss it, we're stuck at Heathrow overnight.

Anyone have thoughts on any of these? I realize we're also talking 9 months out, which means schedules on any of them are likely to change either in our favor or against us with no way of predicting. Thanks.