2 questions about sleep

I have a 3.5 year old and an almost 2 week old. The newborn was waking up at night very consistently every 3 hours from day one (doctors all said it’s fine) and two nights ago was waking up every 4 hours. The 3 year old was taking 1.5-3 hour naps most days.

Question 1: we are trying to transition the newborn to his crib (he was sleeping in a swing or our arms). I’m trying to be consistent with sleep location, so I’m trying to have him nap in the crib as much as possible. Since he typically only wakes up to nurse or be changed, I feel bad that he is spending most of the day alone in his room. Having said that, he is fighting sleeping in the crib and will go for hours fussing or crying resulting in me holding him for those hours trying to soothe him so he will sleep anywhere. Should I keep trying to get him to sleep in his crib (he does the same thing in the pack n play and bassinet) or is it more important that he sleeps period?

Question 2: Our 3 year old is now completely resisting napping and will scream when put in her room even for quite time. Typically I have let her cry it out, but her brother’s room is right next to hers, and she wakes him up. This results in him being awake but exhausted for hours. She will also become exhausted and moody. My husband goes back to work next week and I don’t know how I am going to manage nap time Hell. At this point I’m thinking about just having the 3 year old skip naps, but I don’t think this is a good solution. Thoughts?