Some constructive criticism. If this list doesn't do as well as you hope it does. Please consider the amount of points you have spent in marks and icons for the
csm. What if those points are used to buy more
csm?
https://www.youtube.com/watch?v=cpnRwJKwYC4
Your list is interesting because it reminds me of Black Legion fluff of the Oath Broken warband. That warband is composed of outcast dishonored ronin marines. They get no support from daemon engines or daemons. They get no mauler/forge fiends, defilers, drakes, hellbrutes, terminators.
If you are limiting yourself to just marines may I suggest Crimson slaughter?
All your units get fear? Or was it just possessed?
If your list does not work out please hear me out.
Lord sitting at
ADL+Quadgun-165
10
CSM, This squad joined by Lord. Autocannon and a flamer for overwatch bbq-155
10
csm, 2 meltaguns, champ with meltabomb, IoV, rhino-225
10
csm, 2 meltaguns, champ with meltabomb, IoV, rhino-225
10
csm, 2 meltaguns, champ with meltabomb, IoV, rhino-225
10
csm, 2 meltaguns, champ with meltabomb, IoV, rhino-225
10
csm, 2 meltaguns, champ with meltabomb, IoV, rhino-225
total=1445
Now all you need is a death star to drive that wedge into your enemy as the rest of your 50 marines follow.
Maybe Spawns? Bikers?
If you pick bikers
Equip your lord with bike, powerfist+power claw, sigil? Maybe
MoN. Take him from the home objective holder team and give them IoV for fearless.
Max biker squad, 2 meltaguns will now accompany your lord. Could possibly spend excess points if any on Daemon Heart and BOR.
But for 300pts, can Chaos get an Imperial Knight Ally? You would need to drop some IoV to get 75pts more to get the Paladin Knight.
Or 3 hell blades.