From a first glance these items seem pretty fine (If a little lean on the stat side). Making them vitality items (by far the most competitive item slots) also seems they'd have issue with viability, especially if they would be keeping their low stat lines.
I don't think the platform should grant or be tied to a bullet shield effect. Should just have a normal duration, one that's also a little longer than 4 seconds. I'd also put it in another slot category, like spirit.
Moth wings is really nice. Give it some bonus health, a little bit of a combat stat (fire rate imo, though I could see an argument for spirit power) and I could see it fitting within the game pretty well. It's probably one of the better concepts on this forum, and one of the more likely to get added into the game.