How do I sell my songs to successful artists and receive royalties?

When it comes to idea validation, get testing now. Pick a few artists from different forms of entertainment and see if you can start making them streams of revenue with your idea. If you can, great. You now have case studies to work with. You have something robust to pitch. More importantly, you'll have validated your idea and this will give you confidence to explore how you can upscale your work.

I don't know any specifics about how these companies do things, but this part of what they do doesn't seem like it'd be especially hard. The various music service APIs provide ways to search their libraries for a string so you could do a reasonable first stab that way. Youtube's API provides the metadata so as long as the video has accurate metadata you can search on that.

I would suggest spending some money and cash hanging out at bars where some of these bands perform, Also, try to find a way backstage to talk to the musicians after they perform to do your research. If you're going after well-off musicians, contact their agents or band managers. They are always looking to make or save more money.

A fresh game plan is key. I've been there. Every artist is different. I'd suggest creating categories for the level each artist is at. I look at them as race horses. Each horse daily changes its location around the track- until someone wins at something. Managers have a super hard job of constantly keeping things moving and networking with the right people. But you have the challenge of keeping your artists happy whilst being realistic. If we had a call I'd like to suggest we do an audit of a day in the life of you. What are all the moving parts you have going? What can you do to create a structure and a simple action plan that will help you and your artists get some real wins. This biz is tough BUT I can help you get clarity.

While I don't specialize in band management or promotion, I have some second-hand advice as my boyfriend is a signed musician to a major label. From my understanding of your question, it sounds like they have some sort of following already - from here, I'd identify within the US or Europe where you strongest following is - then target that area first for a more local-focused tour. For example, an LA-focused tour, New England or Midwest tour. This will help keep costs low while creating more fans that can act as band promoters. If there is no following at the moment, you should consider shopping the band and their cover for press coverage to some major music blogs such as pitchfork, ear milk, indiecurrent, etc. Here is a great list of music blogs: http://www.digitalmusicnews.com/permalink/2014/03/26/20blogs. I also know that Perez Hilton often writes about covers that he knows will resonate with his readers. You could also identify music tastemakers for their style on Spotify and build a relationship with them to see if they're interested in including the band in some of their upcoming/new playlists. Many of these folks like being the "first to" knowledge and up-and-coming bands, so this can be a great and sort of easy go-to. Find some of the influencers who are a little lower down on the influence-scale (think a 6 or 7 instead of 10's like Pitchfork) and see if they're interested in interviewing the band via Skype, in person, or would provide coverage for "first access" to new releases. Great examples of these blogs are are "We Found New Music" or "Obscure Sound." Lastly, you could always try to have them signed to a booking agency that best represents their style. Some examples are Windish (https://twitter.com/windishagency) which is large and known for more indie bands. A some new ones like Boston Music Scene (https://twitter.com/bostonmusicscne). I hope this helps! Promoting music now-a-days is a totally different beast from what it was several years ago, but there are more channels/mediums now, which create more opportunities for them to get heard. Good luck!