I agree MS is going to be tougher to get to the guilty verdict.
Here's the case against MS:
1 He actively participates in the testing of the incinerator
2 he talks about bringing something with bones or a dog (no matter the reason for the thing, there is no reason to test out bones - even if its for animals - there is no need to destroy the bones)
3 we know MS needs money, what does an animal incinerator do for him in terms of earning him money (he can't drive)
4 the spliff talk - does point to him being aware of the spliff and what it is
5 the ipad - he is asking for DM's apple id the very next day and MM is taking pictures with it on July 5.
6 the rap
7 him telling kids he killed and burned a girl
Definetly not as strong as the case against DM but it is there. Question will be what does the jury consider reasonable doubt. Also depends on DM and his defense. He's screwed so he may just throw MS under the bus.
I numbered your points so I could respond accordingly.

As I see it:
1 - yes
2 - I don't think he thought it was for animals, but a trial defense might try it. He does suggest a dog, not a homeless person, and even if it is for animals one doesn't want copious animal skeletons left over to dispose. If I was kidnapped by aliens and had my mind rewritten and suddenly wanted to incinerate animal carcasses, I would have absolutely no idea how a previously living thing might change or not change in a fire. It's not necessarily intuitive to know how body fluids might impact the fire or what happens to hard things like bones and teeth. I would want to try something "wet, with bones" to learn and understand.
3 - just more work from Dell, like painting or cleaning
4 - spliff talk is super hinky - or at least it seems so from here. As in the Bosma trial there are things we may be over emphasizing because we're relying on tweets and filtered information.
5 - ample evidence that he was given the iPad - he's not charged with receiving stolen property, he's charged with murder
6 - rap, to me, pretty much seals the deal on him knowing he incinerated a woman. But he's not charged with incinerating a woman, he's charged with murder.
7 - conflicting stories from young witnesses drinking peach schnapps. How do you decide which one to believe? Did he say killed and burned, or did he just say burned? Either way, the possibility still has to be set against the evidence because he could just be trying to seem cool and powerful - as one of the witnesses had concluded before he knew a woman really was missing.