Camping and City Beach hostel are 2.5km away. Campus and Spot hostels are basically halfway between the camp and the fortress and really close to the bridge where the festival unofficially starts. I haven't been in those 2 in Novi Sad but some other student dorms are perfectly fine so I can imagine those are too.
About travel, if you want to go to Bosnia find blablacar or taxi van, I used Gea Tours several times for Belgrade - Zagreb and it was perfectly fine and they go to Bosnia too. You have a lot of old towns, cities, mountains AND amazing cheap food. Romania is nice too but everything really worth seeing is on the eastern side of Romania far away from Novi Sad.