What is actually 'normal' sleep for a 4-5 month old?

Working dad here. Wife is a SAHM. I feel very poor for her because she's up what seems like all night with the baby. I've offered many times to get up and try to share the load but she said it wouldn't make sense to make me tired for work since I can't help feed and she'll have to be up either way.​Our baby is sleeping probably only in 2hr segments. Sometimes we get lucky and he sleeps 3-4 hours at a time but lately it's been fairly rare for that to happen. When is a good age to move him to the other room and start to let him 'cry it out' at night (if that's a thing?)? Would this be a better question for the doctor or are there general rules of thumb as he starts to get older? Should we try making it warmer/colder on the thermostat? Anything else we should consider as pre-bedtime rituals or other things to know for the middle of the night?​Please help! My wife is very hard working but I feel very poor for her and just want to help in anyway that I can. via /r/Parenting http://bit.ly/2DAImO3