1. Both Helbrecht and generic Chapter Masters are playable choices. As you correctly note, Helbrecht won't be as much of a beatstick, but he'll be cheaper and will help the army out more. While Helbrecht is vulnerable to Power Fists, you've got
LOS! and your 4++, and Helbrecht doesn't have to accept challenges. You probably never want to run the Emperor's Champion. 25 points more gets you a Captain with the Burning Blade and Artificier Armour which is so much better it's not even funny.
2. You don't want to run your Warlord in a Land Raider with Honour Guard; it's not so much putting all the eggs in one basket as putting the entire farm in the basket. The Honour Guard will murderize stuff just fine without your Warlord, who is then free to add some oomph to other parts of the list, this muddling up target priority for your enemy.
2a. The relic banner has the advantage of not having to spend an
HQ slot on a 2-wound
IC, as well as being cheaper (and on a 2+ armour model). The disadvantage is that it's on a non-Character and as such can be sniped. I'd probably go with the "normal" banner, 65 points is a lot.
2b. I'd run him with an Axe (or possibly Thunder Hammer). Almost everything that's AP2 is I1, so you'll probably get to swing before dying, and against Swords and Maces you have your 2+. Then again, if you go for a Sword you can always hope to Rend the enemy to death in Challenges.
2b. (again? Wut?

) I'd probably not buy any Relic Blades at all; if you get in a good charge with Honour Guard that's an awful lot of Power Weapon attacks. Chances are you'll mangle the enemy pretty hard anyway.
3. With the increase in cost and loss of Furious Charge and Rage, Assault Terminators seem rather shoddy now. I'd probably leave them at home.
4. What you're missing is that you've got a reasonably resilient Troops choice that can get two Power Weapons. You could also add a Chaplain for rerolls. A blob would be an excellent place to put Helbrecht, as he'd have plenty of people to
LOS! anything dangerous to, while being able to give the blob Furious Charge and Hatred for a turn.
5. The Lasplas squad is a veteran from the old Codex that is still standing strong.I tend to not use a Transport for mine and just plop them down in terrain on an Objective. Sure, there's Heldrakes and such out there, but if they're killing Lasplas-squads they're not killing my
CC units.
5a. If you do buy a Lazorback you'll probably want to start shooting straight away to maximize your firepower.
6. There's plenty of decent long-range units, but I wouldn't take
ML Devs. Lascannons are only slightly more and better at everything except anti-horde, which you probably won't need much help with. Stormtalons are rather interesting in that they're good fliers without being
OP, and not too expensive.
7. Ironclad Dreadnoughts are perfectly playable, but (as you've been touching at) you can't just drop them straight into the enemy lines and expect them to live. They're excellent when dropped on a flank (and as you say preferrably behind terrain or the Pod itself).
7a. The Deathwind launcher has never been very appealing to me. It does wound Tau and Eldar on 2s, but that's about it.
Once you go Black (Templars), you never go back!