Hi Kim,
I would not recommend letting your bub cry for any length of time on their own, especially at this young age. He only has needs at this time in his life whether it be for food or comfort or whatever. Even just 20 mins is a long time to a young infant. Tracey believed there was always a gentler method than lettin oyr baby cry, we just had to find it.
OK, so I didn't realise your wakings weren't at the same time each night. If the timing of the wakings are erratic it is likely hunger thats waking him. not the best news I'm afraid but most likely. W2S is implemented for habitual wakes, these tend to happena the same each night. Sometimes to the minute. This was my DD!
He is still so young and everything is still so brand new. I can remember the frustrations well honey, it aint easy.

Are you sure the reflux is well controlled?
Re starting the day at 7. Well thats just a recommendation. Not all bubs want to start their day at 7! In these early days there is rarely structure to the days but it does come eventually I promise you.