Questions in the following 3 simple sentences.
1. Inevitably in something this big, there are going to be places where things fall short.(original)
Question: Is the original grammatically correct?
I don't understand the meaning of the " something this big " in the original, so guessing it as: something like this big , or "this big something"
and the ""places""? really real places?
What is the meaning of the original?
2. The answers are such that they are likely only known to the enrolled student.(original)
Question: I understand the original this way:
The answers are such answers that
the enrolled student likely only know them(=the answers).
3. Michael, fool as he was, completely ruined the dinner.(original)
Query: I guess the original this way:
Michael, though he was a fool,completely ruined the dinner. Is my guess correct?
Is my guess correct?

Question

Questions in the following 3 simple sentences.
1.  Inevitably in something this big, there are going to be places where things fall short.(original)
Question:   Is the original grammatically correct?
I don't understand  the  meaning of  the " something this big " in the original, so guessing it as:   something like this big , or "this big something"
and the   ""places""?  really real places?
What is the meaning of the original?
2.  The answers are such that they are likely only known to the enrolled student.(original)
Question: I understand the original this way:  
The answers are such answers that 
the enrolled student likely only know them(=the answers).
3.   Michael, fool as he was, completely ruined the dinner.(original)
Query: I guess the original this way:  
Michael, though he was a fool,completely ruined the dinner. Is my guess correct?
Is my guess correct?

Answer

Grammatically fine. Yes, this big thing. We don’t know what it refers to, as we can’t see other sentences. But it refers to something very big. And places here refers to times, occasions, moments, timelines, in the process

I have decided to start my own business. Inevitably with something this big (something as big as starting a new business), there will be places (moments on my journey of creating a business) where things fall short (don’t succeed)

Answer

1. "something this big" = "something big like this"

2. "such that they are" = "answers that are"
   "known to" = "known by"

3. "fool as he was" = "being a fool"
    your guess is not right.  "because", not "though"

Answer

Part 2. Only enrolled students will probably know the answers

Part 3. Because Michael is a fool, he ruined the dinner