1. 65lbs is probably good. The rough estimate is 1.5 to 2.0 lbs per gallon, so you're close to the low end. But it really depends on how dense the rock is and what you want your aquascaping to look like.
2. With the fully cured live rock, you might not see any ammonia at all. If you start seeing an increase in nitrates, with no ammonia or nitrites, then you know your bacteria is doing it's job and you're about as cycled as you're going to get. (This is how my tank originally cycled as my LR
was fully cured also.) You either have that scenario, or you'll see a slight bit of ammonia that will quickly go away. I'd continue testing for ammonia, nitrites, and nitrates just so you know where you're at.
3. Sounds like you got a freebie hitchhiker! The crab will not cause issues with the cycle. If you do end up with ammonia or nitrites during the any cycle that might happen, it might cause issues with the crab as inverts can not tolerate these as much as fish can... which isn't much to start with.
4. I assume you mean the LED
lunar lights? I leave my lunar lights on all the time, 24/7. My lighting cycle goes something like this:
before 9:30am - all lights off, except for lunar
at 9:30am - actinic (blue) lights come on, lunar still on
at 10:00am - 10k (white) lights come on with all other lights
at 8:00pm - 10k lights go off, all other lights stay on
at 9:00pm - actinic lights go off, lunar lights only thing on
Most people leave their main (10k/actinic) lights on for 8-12 hours depending on their lighting needs. The longer the light cycle, the more chance you have in having algae issues.
Sounds like you're on the right track with everything. Being overly cautious is not a bad thing in this hobby! Taking it slow and easy in the beginning is a great way to start, and a great way to continue.
Oh... and welcome to Aquarium Advice!