As DCDEC said, regardless of the lacquer used the OB gloss will yellow, less so if it is bathed in sunlight during the day.
The most durable clear lacquer that I have managed to find is this one
(AC2)
It is the only one I have found thus far that is suitable for worktops. Unfortunately it is a two part acid catalyst lacquer that uses isocyanates (which are pretty harmful to breathe in).
I have worktops to restore in a couple of weeks and will be using it but have not used it thus far. Although I intend to spray it on it can be brushed.
Acid cats (when sprayed) are normally touch dry in minutes and can be rocoated after an hour or two, meaning that items can be finished in a day.
Personally I would be willing to brush it outdoors whilst wearing a charcoal filter mask BUT ISOCYANTES CAN TRIGGER ASTHMA (even in people that had not previously had a history of asthma). Most sensible people would not work (spray) with AC without a clean air supply face mask, brushing however is less of a risk because the AC is not being atomised and bouncing off the surface.
Before even considering it, i would contact the supplier for advice. The AC may "eat" the gloss. I have used exterior AC over OB gloss without issue in the past but the gloss was a couple of years old.
To be frank, I would probably recommend sanding the gloss off and using a pigmented (read: white) AC laquer. It will not yellow and wont require a clear protectant coat. I appreciate that you have spent both time and money on applying the gloss but as you are aware it wont stand up to daily use and as DC said, it will yellow.