OP, is your son happy and content with his life?
That’s the question to ask yourself.
If he is, you have done a good job and now need to give him a bit of space to get into his own rhythm of life with his partner. He doesn’t want to be tied down to your routine because he is building his own. That’s the way it should be.
Be pleased for him that he’s making his own way in life.
The less you pester him, the more he will be likely to come back when he wants to. At least you will know that when he comes to see you, it’s because he really wants to, rather than out of a dreaded duty. You wouldn’t want that !
Continue with your own suggestions for you to go to them sometimes or meet half way for a nice meal and catch up, but always read the room and don’t take their availability for granted.
Invite him for very special occasions yes, (not the Friday night takeaway) but never assume that they can make it.
Whenever you do see you him, let him know how delighted you are to see him but never burden him with guilt that you miss him.
He has his own life to lead.
Hopefully, he will come to share some of your own strong family values when he has his own family.
As for his partner, concentrate on the positives and be happy he has a solid relationship. It’s a shock for you now he has got his own Friday night routine with her, but do everything to genuinely love her and nothing to alienate her. They are a couple now. It can be hard to accept and adjust down your expectations, but you must.
The internet is fantastic for making me feel connected with our two sons and their partners overseas. I send the odd funny/lovely/interesting photo or newsy message about own lives to help them feel connected, always keeping it light and easy. eg. ‘Have a great weekend! we plan to work in the garden then go to the pub for an early dinner.’ They always respond positively even if only with an emoji. And of course there are plenty of face times when they have time.