This is a different bike than the one the thread was started for, as it's the long tail frame rather than the original.
The lock would mount to the bosses between the steering stem and seat tube, (red circles below) if you don't have a bag mounted in the middle. I think that's the controller circled in blue. If so, that's not a very good use of space. That's where the lock is mounted on my Lectric XP Lite. They should design a combination controller mount/lock holder, in my opinion.
Yes, they've apparently moved from cutting out the end of a one-piece grip to having an end cap. However, they didn't want to scrap however many thousand manuals. (a stuffer sheet would've been the classy thing to do)
That's awesome that they're sending you a 2nd charger for free; that's about another $50 value. I had a similar experience with Lectric when I JUST missed their free lock promotion. They sent it to me as a gesture of goodwill. Then you know what happened? I took two folding eBikes with me on a road trip vacation, and the one with a cheaper cable lock got stolen, where the Lectric was safe because of its better folding lock. I will never forget that.
As for tire pressure, you can vary it, keeping in mind that lower pressure will give you a nicer ride at the expense of rolling resistance and range. I'd probably keep the rear at 30 and the front at 25, except when you might be concerned about range.
I mostly agree on your battery state-of-charge thoughts, however, the general guideline is to keep them between 20-80% state of charge. (30-60% for long-term storage only)
It think it's time Lectric sourced a dual charger: two outputs from a single brick. There's too many cords otherwise and there has got to be some cost savings from only having to include one input cord and one housing. Make it an at-cost add-on option.