Peloton 97 is very good. Peloton 240 is a wind resistant layer but not terribly warm when static.
I also don’t think merino does a great job of insulating.
I would go peloton 97 next to skin or over a synthetic short sleeve, heavier grid fleece designed to trap more warm air over the 97 or a 200-300 weight fleece, down, synthetic vest (heated vest would go under the fleece), then some kind of jacket with a quiet outer and ideally with wind stopper. You can always add the ptarmigan under the jacket.
Ptarmigan or any 5 oz ish down is only good with a base and mid layer down to 40 degrees after 2 hours or so. Your results are tracking.
Head and neck sounds like you have items but need to start using them.
Add the oversized jacket, mine is an off brand I got from sportsman’s warehouse 10-12 years ago on a sale rack.
Add an insulating or heated vest.
Use the down pants as soon as you get on stand and at a minimum get some insulated boot covers and throw a hand warmer in them.
You may not feel the cold on your legs or feet but based on your layers you are dumping heat there.
Eat on stand, drink on stand ideally warm liquid, flex and hold different muscle groups before you are cold.