That is not all suspicions are based upon, IMO.
MR seems to skip from arrival at the house/Nerf ball to the next morning. Nothing much has been said about the rest of the evening, except "he went to bed early" when in fact he seemed to have slept on the couch, if he was there at all. What did MR then do? Also the story of Dylan refusing to get up does not ring true for some, including me. I believe he was eager to see R and would have arisen. It also makes little sense, IMO, that Dylan was not allowed to go to R's on Sunday night, since MR was busy on Monday morning anyway. MR had to get up extra early to drive Dylan out there. And finally, I can see no reason why Dylan would not have waited until 11:30 for his father and do not believe that someone came to the house and coaxed him away. If Dylan was so groggy and inclined to laze about and not get up, I do not see him deciding on taking off on foot rather than wait maybe two hours or so for his ride.
Just a whole lot does not make sense to me, least of all MR's continued refusal to speak to his ex or his son. If he is not guilty, he is doing a great impression of a guilty person, IMO.
I would be, and will be, much relieved if we one day learn MR had nothing to do with whatever has happened to Dylan. I still will fail to understand his behavior during this crisis, though, which reads as failing his son, to me.