Hi Smithy, I'm looking at your ideas, and I respect how you went through the rules.
The tell-tale sign was how you made 2 six-man squads just to fit more Marines in.
(However, I believe with the new codex, you actually have 32 points to play with.)
I think an important question is: are you sure you're using Ultramarines as per your title?
With so few points, Chapter Tactics are a great boon, so you should maximise their use.
And with Ultramarines, I think you are best served with a mix of Tacs and Assault in
KT:
--- Ultramarine Kill Team ---
6-man Tac Squad
5-man Assault Squad, 2 Flamers (Fleshbane and Shred)
Chapter Tactics: Ultramarine (all doctrines come in handy)
That's 11 Marines so far, with 21 points and 1 more
USR to play with.
You also mentioned the double 6-man squads and Sternguard. Let me show what I'd do.
--- Double 6-man Squad ---
6-man Tact Squad with Heavy Bolter (Ignore Cover or Tank Hunter)
6-man Tact Squad with Heavy Bolter (Fleshbane or Armourbane) and Vet Sergeant
Chapter Tactics: Imperial Fist (for Bolter Drills on all their weapons)
You see what I did there? I got Heavy Bolters just to use Bolter Drills more.
Everybody's using Bolter Drill all the time, it's BUDDA BUDDA party.
(Plus, two Heavy 3 weapons with
USRs really make use of
USRs.)
And then Sternguard is strange as they're Specialists in themselves.
Their problem is, no Chapter Tactics benefit them really, so:
--- Sternguard Deathwatch Kill Team ---
7 Sternguard in a Rhino
Chapter Tactics: Iron Hands (for Bionics and It Will Not Die the Rhino)
The Rhino benefits the Sternguard as 2 can ride in it as a moving pillbox.
It just squeezes by that AV33 rule, but
IMHO still squishy. So let's try again:
--- Sternguard Deathwatch Kill Team ---
5 Sternguard with the Vet Sgt getting Melta Bombs
3 Bikers with 2 Flamers (Fleshbane, Shred, prolly FNP for the Sgt)
Chapter Tactics: White Scars (obviously Bikes, but Sternguard get Hit & Run)
Sternguard with Hit & Run is actually probably the best for them.
They get charged, they survive, break out, then Rapid Fire Special Ammo.
In Kill Team, which is an objective grab, they can Hit & Run
AT the objective.
In conclusion, that's why I suggested that Ultramarine Kill Team. With any other Kill Team combination, you are best served with other Chapter Tactics (Iron Hands so at least they get Bionics, White Scars for Hit & Run). And I really do like how both the rules reflect the fluff of how Ultramarines are very tactical in nature, requiring you to think tactically when to use their one-use doctrines, which will help you with that list.