What action was taken against the person(s) who sexually assaulted you during your school days and did you receive counselling after the event or to address your self-harming?
Were you able to reach any realisation that it was not your fault and you did not in any way deserve to be assaulted because you were less worthy than others, nor did it occur because you had been cursed by fate or by some harsh and angry god that you had failed to appease/please?
Can you remember a time when you didn't feel 'less than' others? Did meeting/marrying your dh make you feel more 'equal'; more 'whole' and more blessed/less cursed?
As I understand it, you had your ds late in life. Did you give up a successful career to care him in his infancy? How old was he when you returned to work?
What is your ds' diagnosis/prognosis? Is he learning impaired? Does he need a wheelchair at all times or can he walk unaided or aided on occasion? Is it envisaged that he will be able to live independently in, say, a group home with resident staff when he has completed his education?
If there has been an elephant in the rooms of your various threads it is the negative thoughts and feelings you had, and may still have, on giving birth to a child with disabilities and you need to know that it's not unusual for parents in these circumstances to feel as if they have failed and to wonder why they have been singled out, as it were, to face this particular challenge, albeit there is no one size fits all answer to that particular question.
Your dh's words were cruel and thoughtless and, although he subsequently apologised and you've forgiven him, they may still ring in your ears and continue to have an adverse affect on your psyche to this day - and beyond.
This may manifest in a not dissimilar way to the story of Job when he clamed 'the thing he feared had 'come upon him' - the more time we spend 'fearing', the more we run the risk of creating a self-fulfilling prophecy of nothing working out as it should and everything turning to dust in our hands, as it were.
It's entirely appropriate for your dh to express his fears to you just as it is for you to express yours to him but, due to those words he said so many years ago, you may fear that if you do so he will judge you unfairly. That is not a comfortable place to be, nor does it engender frank and easy conversation on matters that are closest to your heart. If you feel inhibited from sharing your innermost concerns with him, it may be that you would benefit from joint counselling if you are unable to confide in him without the help of a third party.
At the present time you have two immutables; the care you are required to give to meet your ds's needs and the care your mil will need until such time as she is willing, or her mental/physical health dictates, to make changes to the lifestyle she previously enjoyed.
If your mil has a degenerative disease of mind or body, asking how long she may require care from her family in the form of your dh, may be the equivalent of asking 'how long is a piece of string?' but you may find it more bearable if you accept that your dh's loyalty to his dm is such that he's likely to 'run around after her' and that she will most probably arrive on your doorstep at unexpected and inconvenient times for the foreseeable future and try to go with the flow.
If you allow any feeling of being 'less than' to determine your response to your dh's absences from your home due to his dm's demands, it's likely that your dh will accuse you of 'giving him more grief' and of being uncaring of him/his dm and this will inevitably widen any gulf between you.
As you only have a short time before mil's return, I would suggest that you attempt to get your dh on the same page by telling him that until appropriate measures are put in place for her, you will give him your wholehearted support with the proviso that you won't hesitate to call time if it appears that either his or your own health is suffering from this additional responsibility.
IMO no feelings should be 'denied or squashed' but if they cannot be resolved, and if counselling is not an option due to shortage of time, they are best written down and not dwelt on until leisure allows them to be studied at length.
I haven't written half of what I intended but as this has been another very long response, I'll end here and recommence later today/tonight/tomorrow. In the meantime I hope you'll enjoy what's left of the weekend with your dh and ds while you can at least rest assured that you won't be sharing it with one particular visitor.