It's great to hear you're both doing so well!!!!!
(Aside to Roberta, who is your biggest fan, btw: Your bunnies are bored with your meals as described. They now have a standing reservation at the Ritz-Carlton. They will invite you as long as you bring your credit card.)
I digress. Re the hay: first, a bunny will eat its hay last usually, when presented with tasty greens, fruits, etc. So it makes sense that Rufus is eating his hay only at night, which is fine as long as he is eating it. It should be unlimited in his hay bin, so you may never see him finish it all, but that's OK too as long as you add fresh so he goes back for more.
It is also likely that he would prefer the taste of a different kind. Mine likes Mature Oat hay best, then regular Oat, then a blend (that BB sells), then Timothy, and finally Orchard Grass. She goes from dry to soft in her taste preferences. I've noticed that most bunnies are the opposite, though, and love the softer hays like Orchard Grass or Second cut Timothy, and may not care for the dryer type.
So buy very small quantities of different kinds and see which one he gobbles up the most. Again, give it to him when he's hungry and doesn't have a better choice. It's like serving dinner before he gets dessert.