1) 18mo, she self weaned when I tried to upsize her pacifier.
2) Can’t advise.
3) My LO’s teeth looks fine to me (she’s 25mo).
4) When mine weaned off pacifier (hers was an immediate wean), she didn’t look for it anymore so I just kept all pacifiers out of her sight. Soothing wise, no issues when sleeping, but when she’s making a fuss like eg. Outdoors, offer toys/snacks, if LO can understand what you’re saying then talk to them.