After reading everyone's comments last night I decided to transfer rather than racking at this time.
Racking is often considered siphoning, but it's transferring wine from one container to another by means that may include siphoning, pumping, or pouring.
I added 2 Tablespoons of mango juice....... am hoping I did not entirely blow it.
Adding anything containing sugar will probably lead to a renewed fermentation. If you're referring to flavor? Blending is a time honored tradition in winemaking!
Also, when the liquid was transferred, there was a layer of cream coloured ???? stuck to the bottom of the first gallon jug; my guess is it was settled yeast.
The thick sludge is a mixture of fruit solids and yeast hulls. You want to leave it behind.
So today, the new jug is again at 73/74 degrees F and the 'burping' has dropped from once every 6 seconds to once/minute.
The bubbles indicate activity, which can include fermentation and degassing (fermentation done, but wine continues to emit dissolved CO2). Generally speaking, bubbling doesn't provide useful information. In conjunction with other things, such as a hydrometer reading, it can indicate fermentation is continuing, or (if the SG is low enough) that the wine is degassing.
Do you have to wait for the sanitizer (I used Star San Sanitizer) to air dry completely before you use the measuring cup or whatever?
No rinse sanitizers such as Star San and K-meta solution are exactly that -- no rinse. Just shake off the excess. Note that other sanitizers do require rinsing -- if you try a different one, read the package!
K-meta solution is produced by adding 2 to 3 Tbsp K-meta (Dave defined this above) and 1 Tbsp acid (tartaric, blend, etc) in 1 US gallon water.
should I have used some of the fluid to break up the sediment at the bottom of the jug and then transferred it?
Absolutely not! As mentioned above, it's fruit solids and yeast hulls, and all you accomplish is diluting your wine.
Should I be adding something to the present brew to help it re-activate? Some kind of syrup?
Monitor your SG over the next week -- it will probably ferment.