I insulated a couple of crawl spaces with Core Foam during new construction. I like the product. Yes, you'll get thermal bridging through the block webs (which you have now,) but you'll get an overall reduction in heat transfer through the wall which is your objective. That said, most spray foam companies have a minimum to show up at your door with their spray rig. If it's a small area it will cost a fortune to use spray foam. Plus, you'll need to patch and paint the holes in the block. I suggest you consider applying rigid foam on the interior side of the wall and cover it with gypsum wallboard.

Second the notion of rigid foam. The R value of the concrete is negligible and that makes up at least half the wall area so the thermal bridging will be a big issue. Even just an inch of foam that is continuous over the wall will do more for a fraction of the price. (2" would be better)