RE: How many are there actual people using steemit? (not bots)?
I'd stay away from spamming people; I hate spammers, so you trying to do the spamming strategy will probably not work out well for you. Plus there are loads of powerful bots that vote you down when they see you are spamming people accounts with similar things, and this can make your Steemit reputation tank (Not sure how it would work with sending people 0.001 SBD though)
I never joined discord because it seemed like an extra step from facebook, which made no sense to me when it was perfectly simple to communicate through messenger. My assumption is since all crypto's have plummeted a lot of the discord people will have focused their energy elsewhere until the price of crypto's goes back up (if it ever does).
I would say try and find Steem people on twitter and communicate with them on there. That way you are dealing with a human and can build a rapport with them on that platform. Then you can start to find real people on here and be a part of it. Hope this helps :-)