Hello Kateedyd, I understand your frustration when it comes to cash parking. First, be patient waiting for your results. It sounds like you have done your homework well and if your keywords are solid, traffic will come. Have you rechecked your keywords since you did your original research? The search volumes can and will change over time. I do not believe that there can be an average income per month estimated on any domain.
If you have good keyword researched domains, I would recommend creating affiliate program sites. They will tend to do better than cash parking and you can drive traffic to your site.
Captain Dave
Free Domain Information