If one says shema and goes to sleep for the night without davening maariv but plans on waking up in the middle of the night should he say birkat hashachar before davening maariv?

Havod Harav, I understand that its best not to say tehillim at night however in our arvit prayer we say some passages of tehillim. Why is tehillim allowed as part of arvit but not allowed if said outside of arvit?

If the congregation is about to start the amidah and I’m only starting the shema and it’s brachot, can I say the amidah with them and then after say the shema and it’s brachot? Is it the same rule for arbit?