I have an old (around 1900) house with a stone basement wall (perhaps 18″-24″ thick). The concrete floor of the basement is 5’4″ below grade. I have two issues that I would like to solve.
A few times a year, during heavy rains, we will get some water in the basement. There is a floor drain that works, but because the concrete floor is not sloped properly (and had some repairs), not all the water goes into the drain. During the typical rain that floods (only a few, very heavy rains), I may get a gallon of water I have to clean up (probably about the same goes down the drain). My workshop is in the basement and while I can keep most of the important stuff out of the path of the water, it’s obviously not the best situation and I’d like to do what I can to prevent the water from entering the basement (if possible) without spending a fortune.
The second thing I would like to do is parge the basement walls to make them look a bit bitter (and to make the basement easier to keep clean; some walls are already parged, those that are not seem to shed sand/stone/concrete dust that collects at the base of the wall).

Water
The solutions (as I see them) are:
1) dig down to the foundation on the outside, put in perforated pipe below the foundation covered with stone and landscape fabric, run the drain somewhere else, repoint the exterior of the basement walls, seal them with some sort of asphalt sealer, and backfill making sure that the ground slopes away (as it currently does). The downspouts all tie into terracotta pipes that go I know not where (which may be part of the problem). The problem is that this is a heck of a lot of work and/or expense (and I’m not sure I have enough room to dig that far down without killing the mature plantings in front of the house and otherwise making a mess of the yard). Also, in order to run the water away from the base of the foundation, I’d have to go a long way into the back yard). It might be easier to tie into a french drain, but if I did that, how big should it be and how should I construct it (is a pile of gravel in a hole surrounded by landscape fabric enough?)

A related issue is how does one determine where underground rain leaders go (or if the pipes are broken)? Is that something you hire drain specialists for? If so, is it expensive?

2) A much easier (and cheaper) solution along the lines of 1 is to simply dig a trench at the top of the basement wall (or down a foot or two) and try to run the rainwater away before it gets to the wall. Since there is not that much water that floods I thought this might be worth a shot (but I wasn’t sure if doing this would then make solution 1 more difficult later if I ever did that). I added wood chips and other organic material around the exterior of the wall to make sure the slope was away from the house (it basically looked flat), and that seemed to help a bit, so I thought that reducing the rainwater might be a sufficient solution.

3)Another possible solution would be to dig a small trench around the inside of the basement wall and simply run that to a drain to prevent the water from getting on the rest of the floor (but not trying to prevent the water from getting in the first place), perhaps using a sump pump or tying it into the floor drain. My concern about this is that it does not prevent the water from entering the wall, so would it then be silly to parge the wall (I’ve been told that trapping the water in the wall is worse than letting it come through, although the sections that are currently parged seem fine).

Parging the walls
1) I would like to repoint the stone walls (the stones are large, some of the wall had been previously parged and seems to be in good shape, the unparged portions have mortar joints that can be dug out with a simple tool such as a screwdriver; the stone seems to be some kind of sandstone, which will shed material if rubbed vigorously). I was planning to repoint the wall with mortar, but and old contractor suggested that when parging the walls, it was best to mix the mortar with extra limestone (or even plaster? cement?) to make it “rich” to allow it to adhere to the walls better. I did parge some walls many years ago with mortar and remember having trouble getting it to stick sometimes (it seemed that if it was the wall to which it was trying to adhere was too smooth, the weight of the mortar pulled the mixture off the wall). I thought perhaps using a screen (such as used for plaster or stucco) attached to the wall might help. So my questions for parging are these:
1) If there is some water (it doesn’t stream in, but rather just seems to slowly accumulate at the base of the wall), is it ok to seal the wall on the inside, or is that covering up a problem that will cause problems later? I’ve had the house for about 10 years and the problem has stayed about the same, and it is over 100 years old, and the basement walls do not seem to have any issues.

2) If I can parge the walls, should I repoint first or clean out the joints, and repoint at the same time I try to make the walls smooth (since the joints would provide a key similar to plaster and lathe)?

3) Should I use something other than mortar to parge them, if so, what?
4) Is using a screen worth the extra cost and labor or a bad idea?

5) And finally, once parged, should I paint the walls with some sort of waterproof sealer?

Sorry to ask so many questions all at once, but essentially they’re all related.