1. So how to measure the difficulty ?
I go through the search results manually, check the first 10 sites manually and see their PRs, onpage seo strengths and then think if my own site is better than them.
I would also do intitle, inanchor tests to see volume of search results.
What else can be done ?
I am considering this keyword for example
install apache tomcat on ubuntu
There are lots of blog posts, upto 5th page that have a post on this topic, and most being wordpress blogs, they are well optimised.
If my own website has a higher pagerank/backlink count than those appearing on page #1, can I still write a post and make it to the first page ?
Most tutorials say that I just need to outperform the first page competitors and the number of competitors does not matter. Mathematically that sounds correct, but is it equally easy to achieve practically ?