Just watch your replays, there's one built-in. Watching your APM live won't really help you as you might strain to increase them for some reason and lose focus on important stuff
Yeah haha you probably would see a low count and start spamming -No point in spamming useless clicks you'll just wear yourself down.
You shouldn't spam unless you are very consistent your timings. I know a few people who try to spam and accidentally forget to build stuff.