Your age difference is a side issue really. In some marriages the love dies between same age couple, when the chemistry doesn’t mach.
In your case the age difference certainly sounds like a big problem , but you have to remember that his interest is still in sex. You confessed that yourself.
When a man is young and virile and like sex he is a womaniser.
When he is old and still like sex he would be sometimes called dirty old man.
I can’t work out why.
However your man is still interested. Tempt him with sex different way and you may get surprised.
My ex (same age) went “mechanical” long time ago. I wanted to communicate…….
In frustration I moved out of bedroom.
You have nothing to loose. Try some spice in you marriage before you give up!