First time in temps below 30s

What pad are you using? Your sleeping pad makes up at least 1/2 of your sleep system and defines all of the warmth between you and the ground. You will want something with an R-value (single pad or combined) of approximately 3.5.

Pad is the full-length Exped SynUL (the yellow one).

If you are using a military surplus patrol bag, you are going to be soooooooo cold in those temps. I used one in the mid 20's but had a fire going all night long. If I didn't have that fire going, I would not have slept that night. 30 degrees is pretty wrong, it's more like 45 for most people.
If you are going to be wearing lots of clothing, you need be sure that you don't end up fitting too tightly into your bag. You will end up pushing up against and compressing the insulation in your bag and the tightness of your bag could compress any of your down or fluffy synthetic clothing. If that becomes an issue, you may need to unzip it and use it like a quilt to keep the effectiveness of all your insulation.

Thanks for the heads up! I'll then take the other part of that system, the black bag – I forgot what it's rated for.

I assume ratings on those bags take into account the fact that the person sleeping would also be wearing the appropriate ECWCS garments.

The pad should be fine as this is what I use in those temps and have been toasty.

Ideally having a sleeping bag with a proper EN rating is the best place to start, but assuming your bag is, in fact, has a 30 degree relative comfort rating then I would probably just bring the 150-weight merino long-sleeve top and the Eldo jacket (you would want this around camp anyway). What about some leg insulation?

Oh, forgot… for legs I have cap2 weight tights as well as R1-like tights. Should be warm enough…

Yeah – for sure. I would take the Cap2's.

My feet always get cold so I will sometimes bring ID Hot Socks. YMMV.

So should I bring the whole ensemble (everything I own?) or just drop either the R1-type top or the Shak?

"I would probably just bring the 150-weight merino long-sleeve top and the Eldo jacket (you would want this around camp anyway)."

At least this is what I would do.

Thank you all for feedback!