I have nothing to offer on the course choice question. The thing I do want to comment on is a bit more general - stress and the management of stress.
I agree with you that excessive mental and emotional stress is not a good thing for a person with MS. There are two aspects to this: (1) external stressors and (2) our own response to stress.
Salim, life is tough. Academic life, working life, family life, it is all tough (and having MS makes it tougher still) and external stressors are impossible to avoid completely. Many of them will be outside your control, whatever you do. And there is a risk that, in trying to avoid stress, a person will decline to engage in interesting things that would in fact be nourishing and rewarding. So I would caution against letting stress-avoidance weigh too heavily in your decisions.
Instead, I suggest you turn your attention to is how you manage unpleasant feelings of stress, and how you define stress. You already have bad experiences of what happens when it all gets too much - no wonder you want to avoid that happening again. It might be worth exploring a little more closely what winds you up and why. Sometimes we hamper ourselves with unexamined assumptions about what we ‘should’ achieve, or the exam results that are ‘good enough’ and ‘not good enough’. For instance, did you really flop your AS levels, as you say in your later post, or did you just not get A grades in them, as an earlier post suggests? Most people would think that ‘flopping’ and ‘not getting A grades’ were two very different things! Do you think that? (With apologies if you really did flop them, of course!) It is worth thinking about whether you are aiming for perfection when ‘good enough’ would do. All I am suggesting is, when you feel the unpleasant pressure of stress, just have a think about where that is coming from and, in particular, whether any of that pressure is self-generated. We can be awfully hard on ourselves without knowing it.
If you have not yet done so, you might find it helpful to talk some of your hopes and fears through with a trusted friend or relative who can listen attentively and in confidence. People can be surprisingly good at listening - if we give them a chance.