I got my 2nd (of my current cats) from the shelter. He was the most fearful cat they had. I took him home with the intention to foster. He calmed down very quickly. I kept him our bedroom in a foster crate at first. The second night he escaped while we were opening the door to change food and my husband and I decided to block off access to the under-area of the bed and just let him be. That night I woke up feeling a pressure on my lower half and when I cracked my eyes open he was there sitting on me. Of course he took off running after that. But quickly after that he got used to me.
It took him a while to come around to my husband (he's more boisterous and talks with his arms) and even longer to come around to visitors but it's 3 years later and he's more social than plenty of cats. He's our biggest lap cat and loves to lick foreheads.
I'm glad you are going for it. Just give it time. Don't make expectations for what is normal or how quickly things should happen. Making friends with a cat is a very zen thing- it's not to be rushed.
He looks so happy in your picture! Thanks for sharing, and I'm so glad that you've had such a promising introduction to one another. May it be the start of a beautiful relationship.