Sky dancer......you say your son has a strict schedule, calling you once a week so maybe he might not appreciate you calling him in between times. Sounds like he has fairly rigid routines, these probably give him comfort so best not to disturb him and disrupt his routine.
However you say you share the same humour.....can you text him funny jokes, memes or pictures. They will make him smile and let him know that he IS in your thoughts, that your whole world isn't taken up with your daughter, that he does matter to you. Hopefully something like that will reassure him a little and help build a rapport between you.
My youngest son and I exchange cat pictures......silly but he loves cats. We also share jokes, videos and podcasts etc. I can go several weeks without seeing him but we are still very close, in contact most days, even if it's just a picture of cute kittens.
When you do talk on the phone try and have lots of nice interesting things to discuss....that don't involve your daughter. Keep his phone time with you, just for him. Encourage him to open up.....his work, what he does with his spare time.....even the tv programmes he watches. Just keep trying to draw him out. Maybe send him a little gift now and then.....it doesn't need to be expensive ......just a little "saw this and thought of you".
Maybe he has stuff going on in his life and he just needs to feel a little bit special and to know that you think about him.
Does he have other worries perhaps and is therefore feeling extra sensitive right now.....money worries, problems at work, just general stress. Maybe he's just feeling a bit fragile, for whatever reason.
Don't feel guilty about the past, it's over and done with, just concentrate on building up a good rapport with your son.