I am brewing some Plumb wine and really need some advice.

This is my first time and I have fermented on the Pulp in a bucket, a
gallon of plumb wine (using greengages from a tree in my back garden)
for about 6 days.

It produced a nice thick cap and I stirred it every day (usually
twice). I neglected to take the gravity at the start (following a
recipe from an ancient boots book that instructed to add all of the
sugar etc. at the start), but all looked ok.

I took the gravity and it was down at 0.992, so I added about 50 grams
of extra sugar and stirred it up, took a reading at 0.994; I then left
it for another 36 hours.

Today there was no CAP and I took the SG, it was down at 0.990, so I
have strained it into a demijohn and added an airlock. But, there is
no gas escaping from the airlock at all, is this OK or have I ruined
this wine by leaving it in the bucket too long or adding the sugar ?

Thank you for any advice that you have.

Best Regards

Steve.