The prime limit is either a number, or a list of numbers like 2.3.5.11, which means all ratios involving 2, 3, 5, and 11 or the 11-limit without 7. Remember to specify the 2 if you want octaves.
The more equal temperaments you consider, the less likely you are to miss something. But this also slows down the search, and if it's too slow the server kills it. The more results you return the slower it gets too.
The highest complexity is in terms of weighted generators per octave, or whatever it works out as. You'll have to experiment with suitable values.
Errors are always the optimal Tenney-weighted RMS ones. You'll have to experiment with values for these as well.