If you want a nice Custard & Apple flavour, FA do one called CustApple which is REALLY nice imo - takes about 2-3 days for it to come through though, think I mixed that at 5%.
I understand Capella do make an Apple Pie concentrate, but I'd get the Version 2 they do - that doesn't contain any nasty ingredients (Acetoin, Diacetyl, Acetyl Propionyl). ALL of the Capella 'V2' range has zero of these nasty ingredients in FYI.
With my Nic base, I decant 30ml into a little squeezy bottle and use that. Ideally you want to minimise the amount of air getting to your Nic as the Oxygen breaks it down,. I have a little undercounter fridge like yourself so I just keep it in there, had it since around May time and it is the same colour as when I bought it - just keep it out of direct sunlight!
For your PG/VG - I can fully recommend
these. Nice big capacity and a huge spout - I just fill it up every now and again when it's nearly empty.
Scales - ideally you want some that measure down to 0.01g. 0.1g is fine for big batches (250ml+) but anything smaller you want some precision ones like
this.
Hope this helps bro!