Portsmouth is not close to rt. 93. There are a couple of routes that connect rt 93 and rt 95 (where Portsmouth is off of) such as rt 101 and rt. 495. If I had to choose which to use, I would go with rt 495. So I will start based off of this.
Yes!! All this!! "local midwives who attend HB, a decent library that offers kids programs, sidewalks!!!, outdoor rec opportunities; parks, nature preserve or hiking/walking trails etc., a natural foods co-op or store, a "town center" or downtown area, misc. community centers that offer activities; like a YMCA, yoga or dance studio, public transportation and AFFORDABILITY." Newburyport meets all of you requirements and is about 1/2hr to 45 minutes from Portsmouth. It is also about the same distance to Boston. However if you want to buy a place close enough to the center of town that has enough land for animals it will be pricey. There are nice area to live in that are not in the center of town though that have land, like West Newbury or Amesbury.
Other towns that come to mind are Amesbury MA, Exeter NH, Portsmouth itself, Haverhill MA (although not nearly as nice). Possibly New Market NH, Dover NH or Durham NH.
Salem, NH has no downtown, no sidewalks and is very commercial/car oriented. Derry is nice, but the commute to Portsmouth will be long (rt 93N to 101E to 95N). I have no input on Wilton, not sure where it is. Raymond and Deerfield also have no side walks and I don't think they really have much else.
I like Kingston, where I live, although we have no side walks, no 'community' but we have land and can drive 15 minutes to get the most. (or 45 minutes to get the rest)
I also posted on another person looking for places near Exeter, NH a few minutes ago. You can check that out too, as the other posters are also commenting on similar things
Good luck and