That's what one of the users in the comment believe, and sounds definitely reasonable (at least the DQMJ3 number). Definitely a bit on the low side, but legs should be good.
No idea. It's really weird. I don't think it's them reacting to bad sales (it started on Monday morning, I doubt you could arrange that sort of stuff in a couple of days.
Maybe they saw the positive reception following demo, and realised they could afford to spare some money for proper advertising?
No surprise for DQMJ3, it's the 3rd DQM game on 3DS, and the... what, 6th, 7th Dragon Quest game on 3DS? Since this one doesn't have any New 3DS optimisations at all, no reason to upgrade either (not even a bundle or anything).
Really curious about Yo-kai Sangokushi. This one will be interesting.