to follow up with dieworkwear's great post (thank you) I can say that I'm the same as you in all of the things you mention - IV in SS shirts and normal knits, M in EO TO TO sweater and Niche Linen shirt, and I'm wearing a III in that picture and is the size I would go with on this particular piece.
Happy that you want to contribute! Easiest way if you're limited to an iPhone is to get an app with an auto-timer (gorillacam or similar), stand with the light source facing you, as opposed to behind you, (very important!!) and prop up the phone somewhere between waist and chest level, depending on the room and distance.
Yeah for sure. Was bumming around town on Saturday and popped in the shop for a minute, and this caught my eye. It's not exactly a huge commitment at $30 either Also RP: tickets to Venetian Snares in Brooklyn, tickets to Venetian Snares in Manhattan