You could try lifting the strips up using a 5 in 1 tool. Another option is to get a wood chisel, and split the wood carpet strips with the grain removing small slivers, once the strip is removed you should be able to scrape the glue off.

Usually the Gardz will prep those damaged areas so that they will not bubble. That's its job. The only thing I can think of is that you didn't remove enough of the damaged drywall so that anything that is loose or moist will pull free with the weight of the drywall compound. All you can do now is cut out the bubbled areas with a razor knife, make sure that you pull any loose stuff away and use the Gardz again and patch it. Sometimes you actually have to do some patching to see where the bubbles will form...it's just the nature of the job.

After sanding, fill in the area with a thin coat of joint compound or spackle. Then sand again and apply a coat of primer. After the primer dries, check your work with a bright light and apply more spackle if necessary. Mark

If your talking about the wall butted against your tub it is a common issue. Tile person should run at least on row of tile or extend tile 2-4" beyond tub. They should also use waterproofing on that wall extending again onto that wall. The lower section of that sheetrock extending from the tub should be waterproofed about 12" from the tub under the molding. The molding itself should be waterproofed or painted with an oil or exterior paint on ALL sides. The corner at the base of your tub is one of the worst water collection spots in a bath and often overlooked in waterproofing. Water pools on tub corners and migrates down. If caulking from tub to walls fails or is done too soon water will migrate behind the caulk into the wall. Most color matching caulks are not silicone. Water migrates down from the thinset drying. Tile persons caulk next day and that moisture gets trapped behind the caulk which isn't water rated. The caulking fails or looses its adhesion. The water then migrates to the area your complaining about. It is not uncommon that when the caulk from the tub top corner to the floor along that wall is cut water will literally run out as it gets trapped. They sell corner guards for tub corners. Check the caulk and redo if needed. Unfortunately once sheetrock gets wet it can mold and deteriorate. It can only be permanently fixed by replacing.