Your limiter settings will depend on your amplifier. Modern switch-mode amplification does a good job of RMS limiting - they can do huge peaks, but the old iron amps tend to beat them when it comes to sine waves for hours at a time. So yes, what are you using to power your cabinets?
The crossover should be low enough to eliminate the out-of-band hash at the top of every TH's passband, and the highpass filter should be a couple of Hz below the last excursion dip. For a THAM15, about 40Hz, 24dB/octave Butterworth.
Chris