FWIW I do suspect holography has something to do with the cosmological constant problem. I think one clue comes from an old paper by Cohen, Kaplan, Nelson (https://arxiv.org/abs/hep-th/9803132). You might find it interesting. The idea is that effective field theory put in a box breaks down when you put in enough energy to form a black hole as large as the box. Which gives a link between the box size (IR scale) and the maximum, cutoff energy (UV scale). Apply this to the size of the universe and you get a connection to the cosmological constant…