Yeah, that's going to be a tough week since the in-person marathon is back on. The RunDisney events run from 1/6 - 1/9, so everything leading up to and including that weekend will get booked. FWIW, you actually have to call them and ask if there is availability. The list that is on the page is only for dedicated reservations in the next month or two.
Because you're going marathon week, I would go ahead and book 2 rooms at one of the All Stars now so you have it in your back pocket. Disney resorts will fill up.