I tried to go to sleep, but my brain is too full of this case and I want to set out the options as to what could have happened, as I see them, before I forget my line of thinking.
Possibilities:
1. Dylan left on foot and met with an accident or wild animal or water, but has not been found. Seems unlikely since nothing was found; his backpack probably would have surfaced by now, perhaps some clothing, as I doubt he would have ventured deep into any woods (or even left the house, since he had a ride.)
2. Dylan set out and was picked up by a local who may know MR is some capacity and either knew Dylan was visiting or saw him close to the house and figured out who he was, offers him a ride, maybe tells him his father knows about it. This person happens to be a secret child molester, as yet not caught, and molests Dylan and knows he can't leave him alive as a witness, as he is far too old. In this case, Dylan is probably not far away and the perp would have been back in his own realm within a few hours at most, no one the wiser, i.e as in Jessica's case.
3. Total random stranger happens by and entices Dylan either from the house or road, into his vehicle, offering to deliver him to friend. Random stranger is a an ex-con, child molester, or some other variation of criminal, and Dylan is either still at this person's mercy (unlikely) or his body could be anywhere, if taken out of the area.
4. Dylan is either taken away, or killed, by a family member, most likely MR, as he is the only one with known access to Dylan. This could have happened on Sunday night or anytime before MR reported him missing to ER. He could be alive, but only if an elaborate plan had been made in advance to keep him away for a long period of time with help from someone, which to me is unlikely.
Is any other scenario possible than these four?
To me, #2 or #4 seem most possible. I don't see #1, Dylan really falling into a lake, or being taken off by a bear, or breaking his leg in some hidden spot where he cannot get help. And I have trouble with #3, the random stranger (not local) happening by at just the right moment. Yes, kids are picked up by random strangers, i.e. Daniel, and Jessica, but bus stops and near schools are perfect places to troll for kids. A lone child on a Monday morning with no one else in sight is not a very likely occurrence. Too much coincidence for me.
Anyway, long and rambling, but I am trying hard to keep an open mind, I do not generally have a closed one. If not for the level of dysfunction in this family, I might lean more toward #2 than #4.
All JMO from my very tired brain...
ETA: I suppose just plain running away would be #5, but surely he would have surfaced if not encountering any of the events in #1, IMO. I mean, where would he go? I don't believe he just decided to strike out on his own. Sounds to me like he had a good life, other than issues with custody.