For those questions, I like to follow paulg's advice:

"Another way to figure out which fields are worth studying is to create the dropout graph. For example, I know many people who switched from math to computer science because they found math too hard, and no one who did the opposite. People don't do hard things gratuitously; no one will work on a harder problem unless it is proportionately (or at least log(n)) more rewarding. So probably math is more worth studying than computer science. By similar comparisons you can make a graph of all the departments in a university. At the bottom you'll find the subjects with least intellectual content."

Do CS.

I did 3 years of both in college through a dual degree program the college had setup with a CS concentration.(dropped out my senior year, but went far enough to give you a general idea)

Keep in mind, this will vary from uni to uni:

MIS from my experience was more about database management and very basic coding skills. It was definitely more business oriented. There was a decent amount of introductory Service Oriented Architecture and other kinds of somewhat technical topics, but it's not really all that relevant.

CS still gives you the fundamentals needed to take on different kinds of system architectures and problem solving.

I by far favor CS as far as what skills will be most worthwhile. You will learn everything you could in MIS as you go along in CS. There's either a lot of overlap or MIS just plain has a lot of lacking skills as far as technical goes.

Despite the stereotype that CS is more academic, lots of those topics are amazing to have under your belt. If you're hoping to get a programming job CS is still the easiest way to get in the door.

If you just want to be a project manager (good luck at entry level) you might get away with MIS.

I would recommend the CS degree with an MIS minor instead. It's not a bad courseload in doses, but overall, to me, not as useful.

I feel your CS pains, I am also having trouble passing Calculus 3(Multi-variable). Math is of course useful to Computer Science, but learning math in reference to CS would be a whole lot better. Not sure if anyone knows any programs were they have Calc for CS majors or not but that would be nice. As to your question IS were I am at is a business major, and not at all like CS. No theory, little programming.

IS is aimed at business in the sense that it is aimed at semi-technical or non-technical roles. Which means it's watered down.

CS is significantly more respected when it comes to engineering jobs. It is also more respected for product management, project management, and the like. Google, for example (extremely selective, obviously), targets CS majors for entry level product management roles.

You should do CS since there's quite a lot of overlap of IS. With a CS degree you can still go for IS-oriented jobs when you graduate (and you may even be considered above people who have an IS degree), whereas it's a bit tougher to go for CS jobs with an IS degree.