How much time and effort do you put into your CS, Engineering, Science, and Math studies?

[AccCreate]

Point noted, I will aim for a 3.3. That way a 3.0 is almost certain.

There are no certainties in life except taxes and death. And even then, at least one of them is uncertain.
Well, I guess you can then argue the only thing certain philosophically is “cogito ergo sum”.

A regular linear algebra course is very different from a proof linear algebra course. The regular linear algebra course is just playing around with matrices. I’m going to assume you are familiar with matrices from Pre-Calculus. A bunch of multiplication/addition. Simple pattern matching at end of day.
PreCalculus as a whole prepares you for Linear Algebra.
Trigonometry in PreCalculus prepares you (vaguely) for Calculus.

No wonder I was confused how you could spend 25 hours on a 3 unit, 2.5 hour per week course.

I don’t understand. Points say nothing about the rigour of a course.
Some of the lightest work I had were 4~5 points. Some of the most difficult work I had were 3 points.
Points don’t say much outside the number of lectures a week.
There are 3 point courses that feel like full time jobs. There are 5 point courses that make you wonder if you even need to read a single page all semester (and why you are paying your parent’s/your hard earned money for such a worthless course).

Is one summer internship enough?

What’s your goal? At highly selective firms. No.
In the average firm, yes.

Originally I planned to spend my summers taking classes.

Try not to spend more money than needed on education especially if you have to work part time for it. Room and boarding adds up quick.
But don’t let “graduating early” be a goal. It’s better to have at least 1 internship and graduate than have no internships and graduate a year earlier.

A couple hours per week studing/hw outside class for Calc I, II, Discret, as in 5 hours outside class or more so about 10 hours for the ‘typical” student

Only you know yourself. I have no idea how competent a “typical” student is.
I would assume 2~4 hours a week outside class to perform a potential ‘A’?
It really depends on the individual at end of day.

I took stats and Pre Calc in high school. But college is more fast paced

If you struggled in those, then you will most probably struggle in higher level courses.
If you didn’t struggle as much in those, then you might not struggle as much in higher level courses.
That said, don’t let a name like “Calculus” worry you. It’s just another math course. Unless your school is named CalTech and forces everyone to use Apostol’s book (which most undergraduates in US would then be unable to graduate), it’s do-able.