Mrsforgetful it's really hard isn't it when you're dealing with a child/ren on the autistic spectrum to figure out after a while how much of it is still a real compulsion on your child's part and how much of it is just habit (yours or theirs).
As you know I have two DSs. The older one, aged four, has a diagnosis of HFA. The little one, aged two, is I am sure not on the autistic spectrum. However the little one also likes his routines and rituals - and can get very upset if something is done "wrong" especially if he is tired. (One reason why I think he isn't autistic is that provided he's not tired, or ill or whatever, I can usually explain to him that there is a good reason why we're not doing something exactly as he expected it to be - with DS1 at the same age explanations just fell on deaf ears.
What I just don't know is how much of this is DS2's own "genuine" behaviour and how much of it is just copying from DS1!
With your DS2, what happens if you have to deviate from the little routines and rituals for a good reason - is he able to accept the explanations? If not, then my totally personal view is that I would see this behaviour as consistent with his being on the autistic spectrum.
I don't quite understand what your MIL is driving at with saying you are doing what you need to do "for an easy life" - I mean, so what if you are?? I always let DS1 go down the stairs first at home - because he has a meltdown otherwise - but the alternative of him having a tantrum on the stairs and trying to push some or all of us downstairs is far worse! I know what you mean about it taking up a lot of time though. Then again my DH who is also a very routine and ritual based person (and who does most of the childcare) actually sees it as time-saving, not time-wasting, just to have the same routines all the time for both DSs - and who's to say he's wrong?
p.s. I don't see anything wrong with giving him cups of tea to drink, as long as it's not lorry-driver strength!