I'm sorry it took me so long to respond. I've had a pretty crazy week! But things are slower now (and my exams aren't for another week lol), so here we go.
If you haven't studied econ before, then I recommend trying to gain some experience with it. I believe Khan Academy has a pretty good course in it, but the videos can get pretty long/boring. My personal recommendation is a bit more off the beaten track: the acdcLeadership YouTube channel has some absolutely amazing videos, with playlists going through both macro and micro. The material is focused on the American AP exams, which doesn't exactly match up with the material we're doing here, but they're a great place to start. By the way, for reference, the micro material is fairly similar to AP Micro, it just goes into the math some more. The macro material is a lot harder than AP Macro, and basically ditches the AD-AS curves until the last few weeks, focusing instead on deriving them with the IS-LM model.
Also, I'm sure you know this, but you can take three modules each semester your first year in up to three (four in my case, since I'm doing a math module to fill the econ math requirement) subjects. If you get in for econ, congratulations, but don't worry about being trapped into it–you'll have other subjects to switch to if you change your mind!
Now for your questions:
1. EC1004 is quite fast-paced, yes. It combines the material from an entire year's worth of classes into half a year, so we covered all of micro before the independent learning week and then the other half after it. I already knew a fair amount of the material, so it hasn't been too difficult for me throughout the year (especially since I actually do the reading!), and I think most of my classmates feel similarly since they have similar backgrounds to mine: you aren't allowed to take the module unless you have at least two years' worth of experience in economics. You would have to take the full-year set of courses, macro first semester and micro second semester. From what my friend in macro has said, it sounds like it moves fairly slowly. We do use a fair amount of math, but it's really just linear equations and plugging things in/moving them around at this point. They always give us the marginal values of things, because student's aren't' required to know calculus for the module. We are required to take either a math module from the math department or Math for Economists, though, so I believe math becomes more complex as the years go by.
2. Student life: to be honest, I was homeschool, so my frame of reference probably isn't the same on this as yours will be. But in my opinion, there's plenty to do. During the first month, I was going to events almost every day: networking events thrown by businesses, trial events with various societies, events put on by the schools I'm studying in, etc. Now that that's died down, I usually go out on average two evenings a week for organised events. That's honestly enough for me, but I have friends who are more involved in other activities and are out more often; I also know people who like to go to the Bop (the main club, I think?) in the Student Union on Friday nights, but I haven't made it to that yet. I'm not a big clubber. People often think there's nothing to do in St Andrews, but I really don't think that's the case. There are people our age all over the place, so of course there are things to do.
3. The teaching in econ is fine. It's a little dry, but very straightforward. They usually have very convenient bullet-point-filled slides up on the projector, then write on the board as they go through the material on the slides.
4. I honestly have no idea what the prospects for econ graduates are. I'm joint honours econ and comp sci, so I just kind of assume things will work out somehow. Firms like Accenture and Citi have held events here for recruiting econ/business students, so I would assume that St Andrews econ students are desirable to companies. Sorry I can't be more helpful with that.
5. I'm in Uni Hall and absolutely love it, and either Uni Hall or Agnes Blackadder would probably be best your first year location-wise since all the lectures are held in North Haugh (you'd only need to go to Castlecliffe, the econ building, for 6 tutorials over the course of a semester). You can try to fill in the accommodation application form with answers that lead to Uni Hall (which is the best hall, of course–no really, everyone says it has one of the best communities!), but you don't actually get to pick your hall. They take your preferences and then randomly sort you into a hall.
Now I'm the one sorry for length, I hope this isn't too long, and that it was helpful! Do let me know if there are any more questions I can answer. Good luck, I hope you get in!