Is there a limit in number of measures that can be added to a Tabular model table?
No I've seen models with tens of thousands of measures in a single table. What you are seeing is just a limitation of the SSDT user interface
How can I add more measures (more than 100) to a table?
To do this in SSDT you would probably have to add another dummy column to your measures table.
If you use a tool like Tabular Editor it does not have this limitation.