I think this is generally a great method of operating for interactions on Steemit. I almost always practice the same strategy. I enjoyed this post, so I'll answer your questions.

1. There are several types of spam. First, there's the new user who has no idea what's going on. They may or may not speak English, so you'll end up with some "nice post" or "upvote pls" comments. Those are just annoying, but don't ever solicit a flag from me unless I see a malicious pattern. I try to comment back and guide them in the right direction, i.e. point them to posts like this one that show them what they should be doing. Then there are the scammer spammers. Take a look at my most recent blog post. I had someone drop a phishing link about a minute after the post was shared. Clearly not a real person, so I was a bit more angry about that one, which you'll see in my reply. That type of spam does get a flag from me.

2. As far as commenting without upvoting, I personally don't have an issue with it, especially if it's a new user, and most definitely if they've taken the time to thoughtfully comment. I can understand that many people don't have enough VP to spread around to all of the posts they want to vote on, and I encourage people to just go comment even if you can't vote, so I like to support that.

3. I nearly always vote on posts that I comment on. If someone has written a post that's comment-worthy from me, I feel like I owe them a vote. I'm fortunate that my SP can support many votes per day, so I always vote even if my voting power is low. It's good to know that you do the same. I like to give value to posts, and I also enjoy giving value to comments. I almost always upvote every engaging and thoughtful comment that is left on one of my blogs. I think it's a good practice that more people should embrace!

Thank you for sharing your thoughts. It's good to know how other Steemians approach these issues.