@Davs - I'm glad you found some of my advice possibly of use, and I'm happy to help :).
Perhaps some or many people don't come back to read replies, and if I leave a "passing through" comment on a blog (that is, a blog I probably won't return to), or a blog I don't follow or similar situation, I don't check back.
But, for the bloggers who I follow and who are interactive with their followers/readers, I definitely come back to check their replies :)! There is a way for people to check a reply box to be notified of comments, but I have never used it.
At the very least, if you reply, then new visitors will see that you are interactive. Another option is that you could email a reply to them directly; I've had bloggers do this.
I actually don't have the LinkWithin widget on my blog...I keep meaning to add it, but I often put links to older posts in when they are pertinent to the current post. So, unfortunately, I can't help you with that problem! I do notice it on other blogs, and I think it's a great idea.
With regards to what jenniejane says about changing the tone of your content a bit so it isn't all about promoting your products, you can easily do that without necessarily promoting other people. I personally like giving plugs and kudos to other artists, including other bloggers, but YMMV.
Here are some suggestions for you: You are obviously inspired by certain music and writers. Are there any contemporary or historical artists you draw inspiration from? Did you come across a really wonderful book on an artist in your library, or is there an art reference book you can't live without? Did you visit an art museum or just learn something new about a historical artist or art movement? If so, talk about that!
Example: in one of my posts of a plein air painting, I included a link to a discussion from Mitch Albala's instructional art blog about synergy between studio and plein air work, as written about by noted landscape artist Matt Smith. Someone thanked me for posting the links, as she was in sort of the same quandary about her work.
In another post, I referenced Carlson [John F. - artist, author of bible for landscape painters] with regards to painting trees after another plein air piece I did.
Did you experiment with a new material or technique that you're excited about? Share your experiences!
Working on an involved painting project? Consider showing in-progress photos and explaining your process - people enjoy reading about that.
All of these things add "value content" to your posts, and will keep people coming back for more.
Also, with regards to posting frequency, I don't think anyone expects artists, even daily painters (of which I consider myself) to post every day. But, just like a plant will shrivel and die if not watered regularly, so will a blog die if it's not fed regularly :). if I come across a blog where there hasn't been a new post in 4 months, I don't follow it. I've "un-followed" blogs that went for a couple of months with no posts, in fact. Do what you can that accommodates your time and schedule, but just keep in mind that if you post infrequently (1-2x/month), you probably won't have the visits and interest in your blog that you want.
Good luck and happy painting!