A1: 2" barlow will take both types, you just need an adapter (which will probably come with the Barlow or you can use the one that you normally use in your 2" focuser)
A2&3: I think University Optics 2" Barlow was around $150. There is a review by Dave (47Tuc) on the site. But if you want to go nuts you can get a 2" Powermate for $450.
