MIP is a non-moving violation, which does not impact your insurance rates. When it comes to the cost, if you're around 18-20 you can expect your premium to be quite pricier than those paid by older folks.
Insurance rates are based on the risk of someone getting into an accident. Since your fiance is legally blind and has a speeding ticket, his rates are going to be higher because of the elevated risk that he would get into an accident.
Insurance companies will ask you approximately how many miles you drive but it is not a rating factor for premiums except in the state of California. California rates on mileage because they see it as a determining factor in how likely you are to get into an accident.
Switching insurance companies won't necessarily raise your rates as long as it doesn't result in a lapse in coverage. Accidents and violations can stay on your record for up to five years, so your past infractions from six years ago should not affect your rates.