I like things natural so would just lift and relay the loose ones then plant thymes and other low spreading aromatic plants between but realise that not to everyone's taste
Once they've raised they're queens to hibernate for next year's generation the workers will die . It shouldn't be too long now, some nests here are already empty.
DG longevity in wooden frames is a bit hit and miss, any water that gets in the grove can't drain away causing seal breakdown. I had a hardwood conservatory and panels broke down often despite what I thought was well sealed
If the building was done professionally one would hope it was done to specs. The barns I've put up have 7x2 purlins 12ft long between the steels but when the sheets are stitched together, screwed down to timber with teks the load is distributed somewhat so for less demanding use/exposure...
If you use too wide a trowel and wet mix it'll spread on to the face of the bricks which will stain them.
When pointing with lime you need to keep working it to keep it lively
Yes, as you hit it with the brush it grinds the surface down so you only tap it lightly .
I don't know the finish your after but old lime pointing has little course bits in it and tapping exposes them on the surface.
I don't know your location but traditional building material suppliers selling...