I have a couple of thoughts.
First, on the food thing, this is based totally on my experience with horses and helping working out "pecking order issues" in a herd, but I think you should set up three feeding stations. There is this truism with horse management that you should always put out "one more pile of hay than you have horses"- i.e., if you have 4 horses in a field together, you need 5 piles of hay available so there is no fighting. The lead horse is always going to try to drive the low guy off a pile, but if the number of piles is arranged this way, there is by definition always going to be one open pile for the low guy to go to. At some point, the lead horse is generally going to give it a rest and the low guy will find a place to eat. I recently went through this problem with my lowest hen too- I explained a little more
in this thread, but the idea was the same, I started adding a lot more feeding options and she very quickly regained her confidence and started eating normally again. She's still super submissive, but she is eating.
On the roosting, I think you might need to physically put Tilly up on the roost a couple of night in a row. I wrote about that in my other thread too, it didn't take long to get my low girl roosting with the rest of the flock.
I'm certainly not an expert, and don't know if this advice will work if there are just 2 chickens vs. a larger flock. But I think they probably just need a few more days to adjust and they will eventually work it out, with maybe a little help from you.