What is the expected time commitment for a part time Research Master's Program? Let's say I get accepted to a Master's Degree Program in Applied Mathematics with a Research Thesis component. If I take 1 class a semester for 6 years and work on my thesis each semester, what could the time commitment for my most difficult semester look like? Assume I am trying to get an A in every class and publish a great thesis.

Does spending 40 hours a week on that single class and research for an entire semester every few semesters sound plausible?
Your planned schedule sounds reasonable, but I would be more concerned about the energy commitment with full-time employment, particularly with a learning disability. Depending on the nature of your disability, the kind of work you do at your job, and your schedule, you might find that you have very little left over for quality academic work after your job commitment. So try it for a semester, but have a backup plan in case you find yourself overloaded. Six years is a long time to run yourself ragged.