Puppiessssss god I'm so broody for a third
He's only a puppy so I'd get the separation training in now, it's not too late and better to nip it in the bud now rather than years down the line! It's a good idea to teach them to enjoy their time spent alone, and making the cage a positive place to be rather than it meaning you are leaving him (going to bed or going out). They come in handy with toilet training too.
I never caged Zena and I wish I had because it made life with Reggie soooo much easier. I fed him all his meals in the cage and got him used to going inside and me closing the door, going upstairs and coming straight back down and letting him out. Started that the first day I had him and he didn't cry at all when he was locked in the cage at night.
Good luck!! I love puppies