a- that number is your reputation. Upvotes from people with a higher rep will make your rep go up, flags from people with a higher rep will make your rep go down.
c- you can post anything you want and use any words you want as tags. Your not limited to the top tags, but they are the more popular ones to use. Just try to use tags that are relevant to your post. If you use tags that are irrelevant to your post just because they are popular you could get flagged and then your reputation will go down.
d- There is all kinds of awesome stuff on Steemit besides crypto stuff. Some of my favorite posts are travel posts, hiking posts, gardening posts, music, art pieces... it goes on and on. There's pretty much everything on Steemit. You just gotta find the people that are writing about the stuff you're interested in.
Hope that helps you out. If you have anymore questions just let me know.
b- @socalsteemit does at least 1 "in real life" meetup every month. And there are more Steemit groups popping up all over the world now.
Thanks for the info! I finally figured out how to find you on Discord. Looking forward to getting to a meetup soon!