@ 150 lbs,IMO, some say a minimum of 1 lb/gal, but 1.5 or better is better yet
and definitely get more powerheads, I have 3 in my 75, plus afilter rated at 300 gph, which I now only use for circulation, and an occassional use of carbon
your desired circulation should be at least 10x's your gallonage per hour, this is a MINIMUM, more yet is better, with corals and stuff like that, alot of reefers will even push or exceed 20x, you also want o eliminate any dead spots in your tank, especially around your rock, wheere are naturally pockets that do not get water flow
not only will your cleanup crew get eaten, but there is also a good chance that they will not sruvive to start with, having highger nitrites this would depend on the particular species
adding cured lr, an or ls now may help to speed up your cycle, but if you add lr now, please cure it first(or buy locally, cured lr, this will help with any die off), other wise you'll go right back where you started from(an ammonia spike that will more than likely kill something), Also if you cure it yourself this will take weeks to months by itself
HTH