Pretty good kit, really. Especially in the context that the OP stated, somewhere between in-pocket and in-pack.

Yes, I would add a mini-Bic. Or even a full-size Bic; the weight penalty is next to nothing. I don't like or trust kitchen matches, based on the gross failures I've seen over and over. Glad to see you have three kinds of tinder (or is that four?).

I'd suggest adding a small roll of super-sticky 1" first aid tape that will stick to skin and stay put. Apply to rub points before real trouble happens. Blisters are debilitating to both physical performance and morale.

I'd swap the paper clips for a handful of all-metal diaper pins (oversize safety pins, all metal, with a sliding lock). These are the maid of all work, even to the point of improvising clothing.

IMO stay with the Heatsheet you have (esp. if it's the 1-2 person size). It's much more versatile, and you can control moisture/ventilation. I don't like bivvy sacks, having first sweated and then frozen in one (not an AMK, but an impermeable bag is an impermeable bag).

Maybe add a dozen hard candies if you have room. Little dollops of energy to boost your morale and energy level just a bit. (Not suitable for bear country if you want the kit in your tent/shelter.)

As for the carabiner, it's perfect for a lanyard to keep any piece of essential gear (knife, multitool, kit bag, or even USB sticks) firmly attached to your person. Each bag or kit of mine has several, always.

A handkerchief is never a waste of space, if you have any left. And a 4x4 or two gives you a sterile layer between wound and improvised bandages.

A black trash bag (untreated), or hunk of black plastic can generate a surprising amount of meltwater. Not at -30C of course, but often there are microclimates that you can exploit. I've found places at -10C where I could melt water and dry my socks somewhat while wearing them.

Plus, no toilet paper? Really? Moss is okay, but spruce tips really crush morale in a hurry.