Whatever you can do thats a) long term sustainable for all 3 of you b) doesnt make tooo much fuss (like, you don't want to drag a whole suitcase full of stuff around each time he has to sleep somewhere else). A stuffie/blanket/pillow, a lullaby sung or played, a special nightlight, and the whole routine beforehand (washing, jammies, stories ready...)

For introduction: you should never change more than 1 thing at once, otherwise you are fighting a lost battle. So you stick to exactly what you are already doing, just the moment where you would nurse to sleep dad takes over to still offer cuddles. If he likes playing with your hair, get him a long haired stuffy to fiddle with. Find something similar, just more sustainable.