People saying autism is a mental illness is one of my pet hates, even a social worker has argued it's a mental illness and I eventually fell out with her because of it and I'm almost frightened to get a copy of my medical files because if I find it on there I will go nuts and it will cause me a lot more stress, but what's much worse is I've been put into housing where I've been mixed with NTs with mental illnesses which couldn't be less compatible with autism, in fact it's caused me all sorts of issues and problems in the past in what was an extremely unstable, noisy and very unpleasant environment for an autistic person, it was utterly ridiculous and extremely unfair. We are BORN with autism, IT IS NOT A MENTAL ILLNESS, it is a life long condition and autistic people couldn't be any more incompatible than mixed with NT mental health patients! I do agree that there are co-morbid conditions that could be considered mental illnesses, E.g. depression, but even then I think depression is often misdiagnosed and then harmful antidepressants are often prescribed that can make matters much worse in the long term. If a person feels "depressed" for a reason it's not in my opinion an illness at all and there is virtually always a reason, even if it's an underlying one from the past that isn't immediately obvious, in the case of autistic people we often find it harder to cope in an NT world and the stresses of this can often make us feel down for that reason. In other words the reasons why people feel down should be addressed to resolve or at least improve the issue, but unfortunately most doctors think harmful mind altering drugs are better because they're a cheap "quick fix" as far as they're concerned, another patient dealt with, goodbye.
My 2nd pet hate is NTs complaining about my autistic traits, it's not so much them thinking it will pass, but they often tell me just to stop them, at worst even telling me I'm doing it on purpose and that I can control it if I really want to. One problem I have is controlling the volume of my voice, I'm often told I'm shouting, but to myself I sound like I'm talking at a normal volume, I've practised trying to talk at what they see as a "normal" volume with a friend, when he says I'm talking normally I can't hear myself properly, it sounds like no-one can hear me and I'm constantly urged to increase the volume, if I was to talk like this all the time I'd have to be constantly conscious of my voice, concentrating on this alone and then I'd be unable to think about what I'm saying in a conversation, I simply can't do it and if I'm particularly emotional about something my voice apparently gets even louder. I've been in various situations where I've thought I was talking normally and I've be shocked to see security called because I'm apparently shouting which is misinterpreted as being aggressive when I am not in the slightest bit aggressive, this happened when I was talking to a receptionist at a doctors surgery for instance and incredibly they simply wouldn't listen even when I told them I was autistic and that I wasn't being aggressive, they just said we have a zero tolerance towards aggression and in the end I had to have a key worker explain to them after I was forced to leave, but I still didn't get an apology, instead they seemed to think I should apologise and all I did was talk louder than "normal" without realising BECAUSE I'M AUTISTIC, NOT BECAUSE I WAS BEING AGGRESSIVE. It is extremely unfair and you'd think a doctors surgery at least would be more understanding of a condition like autism. Another issue is I'm slow at processing words spoken and if a person talks too fast I often don't interpret it, especially if there's background noises. This means I often have to ask people to repeat and sometimes I still pick up words wrong, sometimes people get really annoyed when I still can't tell what they said even after they've repeated it and I have asked them to say it slower. I've had numerous people accuse me of not listening however, telling me that I should start paying attention to them, this is made worse because like many autistic people I find it very uncomfortable to give eye contact. Sometimes they say I should get my hearing tested and I explain that there's nothing wrong with my hearing and that it's slow processing due to being autistic, but I often don't seem to be believed and again I've even been told I'm doing it on purpose. My hearing itself is actually good, in fact sometimes too good and I struggle to cope with certain sounds that I'm over sensitive to that often don't bother NTs. I'm sick and tired of NTs having a go at me because I'm autistic. In fact there's even more autistic traits I could mention that NTs think I should just stop doing, but I will finally mention NTs complaining about me repeating things, and/or going on about things, I try my hardest not to do this, but it's usually automatic and even if I become conscious of it, it's still very difficult because I get a strong urge to speak and repeat, but NTs often get really annoyed at me for it.
Your questions are difficult to answer because I simply don't have all the answers, but most of the problems are trying to fit into an NT world where NTs don't accept us. Regarding obsessions, well some could be used for positive means, for instance an obsessive special interest can sometimes be used very constructively, E.g. in employment or perhaps to help others, depending in what it is.
Yes I think it's possible to extricate myself from obsessive thinking and behaviours especially since I understood these to be a part of having high autistic traits. I am starting to spot the pitfalls quicker now. But the other side of the equation is that some things can be obsessive and ok. Eg, I collect heart shaped pebbles and arrange them on surfaces. It's so pleasing. 
