I think you're greatly overestimating Edwin's value to Chuck.
And I think you're doing the same regarding how much Chuck is doting on Grace & willing to forgive her regardless even if she messes something up or even crosses the line.
Not to mention dismissing how much Edwin & Victoria matters to Ian.
Also, lol you are aware of "discipline", right?
Yes, Chuck raised Grace like a father as you said, but even parents discipline kids when they do something wrong/bad.
Just doting on the children gives them bad habits thinking they can get away with anything.
What makes you be so sure that Chuck won't discipline (reprimand or punish) Grace for what she did?
Grace basically;
1) Told Vicky that she was aware of her porn work past
2) Told Vicky that Chuck has taken MC under his wing like with Ian
3) Blackmailed Vicky into forcing Ian to do what her (Grace) and her husband wants.
To look through them one by one;
1) From how Grace & Vicky's convo went in their meet, it can be said without a doubt that Chuck told this secret long ago when they were young (i.e. when both MC & Ian were much younger I think).
Given Grace has kept the secret this long, it's more likely than not Chuck has told his sister to keep it quiet.
And Grace, out of her desperation to keep Ian in line with what she wants (i.e. send him to college), pulls out the "porn work secret" card thinking it will push Vicky to do what she wants.
And while nothing's been shown yet as to what were Chuck's instructions for his sister, do you really think he would not care whether this gets out?
2) Next, she literally blurts out Chuck has taken MC under his wing.
Now, while it doesn't specifically show that Chuck wanted to keep this a secret from Victoria (from my memories), Vicky finding out that her son is working under Chuck causes nothing but trouble for Chuck's end, given it's unlikely she will have a favorable view of her son working in such environment; especially given how Vicky herself is ashamed of that part of her past.
and.....
3) Blackmail
Grace could have done anything. Literally anything else to try and persuade her son to go to college.
But first she tried to manipulate MC into persuading Ian to go to college (which I obviously didn't do of course, Ian's way too much of a bro for my MC to betray his trust), and when that didn't work tried to manipulate Vicky to do it for her.
Despite Vicky's suggestions of "start things small and slowly move up to persuade" she basically ignored it and brought up the unplesant past and ending with blackmail to force Vicky's hand.
You said, "why would Chuck would give two shits about Victoria?"
lol let me flip that question for ya; "Why wouldn't he?"
I'll give you 3 reasons why he would give two shits;
1) IAN
2) IAN
3) IAN
You placed Grace > Ian, but I see that order is only relevant when only Grace is in the right and nothing detrimental happened to whatever Chuck himself has planned or values.
I can see that order be very much flipped to Ian > Grace if the actions Grace had taken doesn't benefit Chuck in any way or simply put, Grace is in the wrong - and she 100% is in this case.
To add further, no way will Chuck risk antagonizing his nephew that he loves.
That time Ian shuts his mother out (if player's MC told Ian about how his mother wanted to convince him to go to college), all Grace did was just try to manipulate MC. No antagonistic actions were taken, no permanent damage.
Hence, Chuck tried to calm his nephew down with that phone call with "Please talk to your mother for my sake" etc etc.
This situation with Victoria is completely different from that.
Besides, you really think someone like Chuck wouldn't be aware that Victoria was more of a mother figure to Ian, much much moreso than his own sister ever was?
Lastly, you said Chuck and MC are literally strangers.
In terms of biology lol, yes they are, and as you said Chuck only gave that job at the club due to Ian's insistence.
But you're dismissing how much closer MC and Chuck gets over the course of the game.
Sure, it started off as nepotism due to Ian, but the interactions the two of them have become more like a family.
Come to think of it, he even gives a stern warning to Mrs. Pulman saying "I now think of Edwin like a family, so you will NOT push him over to the edge with your antics" (or something very similar to those words) and Mrs. Pulman relents a bit saying "I understand."
Noone would say that about MC if he thought MC was just a stranger to him.
Hence taking everything I said till now into account, to your question yes Chuck would literally give two shits about Vicky.
He may have raised his sister like a daughter, but even taking that into account I'd say there are limits to what his sister should have been allowed to do.
And Grace crossed the line here.
Ignoring it without at least a repirmand or punishment, Chuck would literally be throwing the whole relationship he had been building with Ian & MC away.
I have a strong feeling he won't do that.
But who knows. Only
TD1900 would know given he's the creator.
We're just throwing theories around here at this point.