Thank you for your question. I look forward to working with you to provide you the information you are seeking for educational purposes only.
If the HOA bylaws state that the outside siding is responsibility of the HOA to repair and they are not making repairs, first thing you can do is you can sue them (since they have refused to comply with the bylaws) and seek a court "declaratory judgment" to force them to comply with the bylaws. Ultimately, HOA pay for repairs to limited common or common areas through dues they collect and if dues are not enough to make repairs, then they place an assessment on all members for repairs, so ultimately you will end up paying something for those repairs one way or another.
As far as them changing the bylaws, that is up to you and the other owners to stop by going to the meeting and voting the bylaw change down, keeping in mind that if it fails and you force repairs to be made, the Board can impose an assessment on you and all owners to cover the costs of these repairs. You do, however, have a right to sue the board for a declaratory judgment and seek a court order to force them to comply with the bylaws and make necessary repairs.
AS far as your disability, if you can prove that the only reason they are treating you this way is that disability, then you have grounds to sue the board and HOA for discrimination under the Americans with Disabilities Act and also under the Fair Housing
Act, for which you would also need a local attorney to represent you.