Need help in finishing a gap between countertop back & wall
I have an old house that I actually bought personally sight unseen (I had my mother check it out, and she didn't notice it, but my financial situation was pretty much that I had to buy something dirt cheap and quickly file for bankruptcy shortly thereafter.) Had I seen noticed, I may not have bought it - but whatever, I have it now. I think there were some structural issues with the house before it was shored up that has caused this. The wall seems to have stabilized, but perhaps it is still bowing out very slowly.
Anyway, as the title indicates, there is a long standard laminate countertop about 10' long. At one end, the gap from the edge of the backstop is about 1-1/2" and at the other end, it's virtually nothing (~ 1/8" ?) To rectify the situation, I took long skinny & tapered strips of strong cardboard paper in a V shape and forced it down the gap, then used Great Stuff foam over that, and then plaster on top. I didn't get the plaster very even at that time - as I always intended to eventually even it out by laying up more and more plaster until it would be quite even. Ideally, I would like that gap to be a flat surface parallel to the floor/ceiling, but a slight angle up would not be so bad. Currently, there is also a problem with cracks (some rather wide for a crack at about 1/32") at the juncture of the gap surface and the wall, so whatever I do going forward, I need to remedy this. I should say that I did something similar for the side of the cabinet (which was at the wide gap end), and because I was able to square that off with the side of the cabinet, it looks great (and with no crack, making me believe that the wall has indeed has properly stabilized.)
So, I'm not sure what to do. First, I would grind down (with my Dremel tool) the current plaster & foam about 1/16" or so below the top of the back stop to the wall. ( I think I have enough foam structure under that pretty much throughout.) Then I would place plaster mesh and somehow lay that on the corner. This could work well for the wider gap section, but I don't see how it could do much for the narrow section. Perhaps I should use the mesh up until a certain gap width gets too small, and then do something with caulk? How high up the wall would I need apply the mesh? Perhaps just redo the plaster without any mesh, let it settle and crack, and then caulk it? (If I did that, I would let it settle for about 9 months, since that is how long I always leave to go teach English abroad, and then do a final grinding and painting.)
From research, I see that folks use a backer rod, which I think my ad hoc method of using Great Stuff foam basically emulated. But since such a backer rod would be a standard diameter, I would have a problem using that across the length of the countertop.
I guess that an all encompassing solution would be to just get a new countertop installed being variable depth, which might look a little bit funky (but I suppose not as funky as the fix I am doing), but since it would be varying depth, I just have to think that it would be expensive. But in any case, I don't want to dump any more cash into this house than I need to. If this gap area can be made nice an flat, I don't think it would look too bad, and in any case, if my eventual buyer doesn't like it, he can go ahead and have it done.
I am open for any cheap do-it-yourself suggestions! I have lots of time and not much cash.