Those are all examples of problems learners hit only when they've successfully learned English. By the time a non-native speaker has to worry about subjunctive

Those are all examples of problems learners hit only when they've successfully learned English. By the time a non-native speaker has to worry about subjunctive or less vs. fewer, they've already reached a level of proficiency that allows them to communicate fluently despite an occasional grammatical gaffe. Before reaching that level, however, they have to deal with truly maddening stuff like how to pronounce word like "read" or "tear" or "close", or why it's "an interesting little book" instead of "a little interesting book", or why you can see a movie but you're not "seeing TV", or the fact that both "thir-tee" and "thir-dee" mean 30.