Ok, a few thoughts in no particular order:
1) There are two types of
strobe circuits. One type discharges a
capacitor across the flash tube, the other fires the flash tube right off the AC
line. Neither
play well with dimmers, in fact, the cap type often use a
voltage doubler
circuit which can go into extreme over-voltage when powered with a reverse sawtooth waveform, such as what comes from a
dimmer pack.
2)
DMX is a control
protocol. You can get USB/
DMX adapters (called a
Dongle) and run your show from a laptop. You cannot use the
DMX itself to
power something. The control signal would control a
dimmer pack (for standard lights) or an
LED par, or a moving light. In each case, the
power comes from a separate AC connection.
3) Something is off on the
power calculations on the floodlights. Are you located in a country where your AC outlets provide 240 volts? If so, each of your 150
watt floods would only draw a
bit over a half of an amp. (0.625) Three of them would still be under 2 amps. Most "
shoebox" dimmers can handle about 5 amps per
channel. The
dimmer would have to be able to work off of a 240 volt
outlet. Not all do.
4) 12 volt lamps at 150 watts would not be
practical as they would be drawing 12.5 amps each.