I'm not sure you supposed to use 1 pixel transparent border in TiledBG's, because that contradicts the purpose of tiling in "Tiled" backgrounds.
Never had any issues with seems (except of - wonderful but useless for any not-pixel-retro project (which is a big shame) - Tilemap) and I'm always using 1 pixel transparent border only in sprites and only if they are going to rotate.
And I would suggest to not use scaling that is different then 0.25, 0.5, 0.75, 1, 1.25, 2.5 etc. cause this will always shows some artifacts and in overall will look bad
That's why long time ago (on 2nd September 2011 to be precise ) I've "attacked", but very nicely Ashley about zoom in layout editor itself - using ctrl+mouse wheel gives you strange values like 91%, 83%, 67% which makes objects looks bad and hard to position in many cases. Also I've asked about point sampling in layout editor, which was gladly added in r55 but then it was removed some time later... try to position 8x8 pixel size objects on 800% zoom hehe.