acrylic seam bubbles

If you want #16 go just up the street to Delvie's Plastics.  I've used the Craftic's 33 too.  IMO it's the same as weldon 16 (but I prefer weldon ).  Bubbles are inevitable when using those thick glues, ime.  If I were you I would scrape it out with a razor blade and redo it but put a 1/4" x 1/4" x "however long the side is" piece of acrylic in the corner.  It'll still bubble, but it'll hold mechanically well and imo do a better job sealing.