Let's see, you shoot someone, in the dark, with a suppressed SBR, and you are also concerned about how fast the suppressor heats up? That really, really doesn't sound like home defense to me, and likely won't to the police and the prosecutors, either. I don't think its a very good idea to use a piece like that for home defense, unless its the only gun you own, and even then, its not a good idea.
Remember that even if it looks clear cut and legitmate to you, it may not to someone else. And they will take your firearm as evidence until it is all legally resolved. I'm not trying to knock your choice in arms, only your choice in a suitable application for the one you have. Think what a jury of non gun owners (and the DA) is going to make of it, if you ever do use it for "home defense". They are not likely to be inclinded in your favor. I would expect rather the opposite, in fact.
Ok, sorry, I just assumed you were in the USA. If you are in some other nation where you might face terrorist/bandit attack at home, that's another situation.
In "pitch black" conditions, that means short range, and any effect of a suppressor on rifle accuracy will be negligable. The same for change in trajectory from heat build up. At the short ranges you will be able to identify a target (even with night vision optics) any change in trajectory is also unimportant.
Home defense implies inside the home (again, in the USA), using supersonic ammo with a suppressor removes (attenuates) the muzzle blast. Inside a building, that's all you are going to hear anyway. The crack of a supersonic bullet as it passes close to objects down range doesn't apply inside a room.
You can certainly use the gun as a home defense option, but there are many, many more suitable options availabe...which I think you ought to consider for "home defense" over your present choice.
All else being equal (and it almost never is) bigger bullets tend to work better.