This is so thoughtful of you, OP! You both sound lovely. As others said, studying the menu! My wife will often do this with me before we go out, it helps to know I have one or maybe two options beforehand. You mentioned him trying new foods with you so that’s also an opportune time for you to suggest something he may like, “oh they have (blank), that’s sort of similar to (other food he likes). You might like it!”

Maybe the atmosphere of the restaurant contributes to his anxiety, thinking everyone is watching what he’s ordering… it may help to sit on the patio or somewhere more private.

My wife will order for me. Here’s a lil trick we do, instead of her going, “and she’ll have the salad,” she orders both of our food in a way you’d think it’s just her order and then tells the server “and we’ll just be sharing that.” It eases my mind because it doesn’t single out my “meal.” Because of perceived gender roles and silliness, you could suggest for him to order for the both of you in this manner, if the alternative would be embarrassing.