3 maintenance questions

[tkd]

2007 Nomad w/11k on the bike. I am the second owner. The brakes have not been done. I can still see probably 3 millimeters of brake pad on both the front and the rear and I have no pulsing at all. Problem is the rear (and rear only) has begun to squeal when I stop. Does this sound normal?

Second question. Since I live in MN, the evening can be a little cool (it's about 62 as we speak). I am getting ready to change my oil. Currently the bike has 20w-50 in it, but I'm thinking that as the season goes on, 20w might be a little thick as things cool down. I really wanted to go with Mobil 1 20w-50, but it is nowhere to be found. I can find a Mobil 1 full synthetic in 15w-50. The summers aren't too incredibly hot (probably 85 average) What do y'all think about that.

3rd question. Motorcycle Jacks. Pep boys has one on sale for $69 bucks. Rated at 1500 pounds. Range of lift is 2" to 16" and has 6 lockable positions. Anyone ever used this or have any thoughts.

Appreciate all the help