General rule of thumb is that as you have more variables, you need more trades and more data. As for whether or not you can test more variables on a smaller set of data will depend on the type of variables you have and how the values of the variables change. Base power 11 will give you the number of combinations you have where base is going the range of each variable. You could also simply look through your history to see what value the variable took on, as a basis for number of combinations possible. For example, if on a given day your indicator RZI had value 0 and indicator RBI had value 3 then you could look at this as a single combination, 03. By looking at the number of combinations and using information theory, you could likely come up with some idea of whether or not you have enough data. There are general rules of thumbs available if you search, as well, that come from general statistics. Keep in mind, all statistical analysis will assume a stationary time series which is not the case.
Yes, I think it is reasonable to verify the base strategy before trying to optimize across so many variables.
Common ways of doing this are using an N bars exit and fixed stop/take profit brackets.