Hello Jonathan,
The problems pertaining to the MEP parameters is a question of finding out the right conversions for your units and feeding the parameters the correct object type (usually doubles or integers instead of strings). You could also use one of the custom nodes in the MEPover package that will let you set your parameters as project units or as strings.
The read only error you are getting seems to be correct as most of those parameters are grayed out, meaning they can’t be changed directly.
For both of the above problems I would suggest trying to set a single parameter at a time and then see what error you’ll get and try to solve that single error. Rinse and repeat for every other parameter that gives you an error.