When he is ill, you have to do what you do to comfort him, but the results will usually be that because he is older, you have to start all over and it takes longer, because they have more patience to test you.
If he is not climbing out of his crib, keep him in it if possible. You may need to borrow a crib for the new baby, just so your son can stay in the crib as long as he stays in..
We cannot say it enough that children love routine and constancy. in their schedules and discipline. ANY deviation rocks their world.. They are not verbal enough to explain they like knowing what is happening next on their own..
So you set up the routine and make sure that it stays that way every day possible. This is why parents do not go out very often once the have children.. they know it cab cause a disruption in their childrens routine..
Also start giving him more of a heads up. "We are going to eat dinner and then you will have your bath".. While he is in the bath, explain "after bath we will put you in your pj's and then bedtime story", "after 2 stories, you will go to sleep." or whatever your routine is.. .
While he is in the tub, you or your husband, make his room soothing..Turn down the lights, play some soft music. make sure there is not a lot of loud activities going on in the house during bath time and bed time routine.. He will want to be in the middle of it.. TV playing , cell phones going on, loud conversations.. it has to seem like everyone is calming down for bedtime..
Then a quiet bath, as long as you rile him up, it will take double that time to calm him down out of the bath.
Then follow the routine.. Read the story while he is in his crib with his lovey.. if he has a cup a bottle or breast feeds, let that happen, Some people cuddle their children while reading.. We tried to allow our daughter to lay in he bed with her "puppy" ad she would self sooth by curling her hair around her finger.. sometimes, I would rub her back as I read.. My husband used to be so tired, he would read lower and sloer and actually fall asleep and so would our daughter!
Just figure out what will work for your family, get your husband on board and do it the same way as much as possible.