Dog banging on door, do I need to step up the crate training or is there a different method?

14 week old labradoodle who we got at 12 weeks. We are fortunate to have a spare bedroom and initially kept him in a small playpen with an open crate. Well within 5 days he was climbing over the gate so now we’ve transitioned him to be free in the room but still leave the crate open.

He sleeps mostly through the night for about 6-7hrs before waking up to need to pee (thinking about waking him again around 4hr mark to avoid him waking US up).

Anyways, this was all working out pretty well. We were able to take him into the room after being out for 1-2hr then he’d sleep for 1-3hr. Lately though he’s been immediately starting to whine then BANGING on the door. The only way to get this to stop is to sit in there with him for 15min until he lays down in his cage and gets more sleepy.

Am I teaching him to have separation anxiety by doing this?

Should I start closing the cage?

Should I leave his cage open still but find a physical barrier to block the door?

I’m thinking of getting him a slightly bigger cage so he feels a bit more freedom in there but this banging on the door is driving me insane. To make matters more complicated we have a cat that we’re slowly trying to introduce them to each other so we NEED to put him away often for the cat to be able to walk around the house.