Answers to questions....

1. Light sounds real god and adequate. No overkill here.
2. I wouldnt even use the HPS until week 4.
3. You could have. But if you vent out with a fan like you said, you should be fine.

My concern would be with the 5 foot height. Add in your grow container, lights hanging down, fan and exhaust setup....and then add in your FLOWERING buds....

Better be a pretty low grower. Remember your final product will be at least 2 times the height of your plant, maybe 3.

Allow for it.

The rest sounds good.

HAPPY BOX BUILDING