There is no way to know for sure the real value of H1-H2-H3 tags. Only speculation. My opinion is, just use your best judgement.
I was told that META descriptions aren't relevant in terms of keyword density however I know they play a big role in click factor (people read it and then click or don't click) and google has once said that click factor does matter. So that is something to consider.
The age of your domain has long been a factor but not as much as people would have you believe. Plus there is a limit. 3 years, 5 years, 10 years - all seem to be the same - "aged". I think what matters here in terms of age are domains under 1 year. I've been trying to figure that out and from what I can tell there are three categories - baby domains (under 1 year), domains (1 to 3 years) and aged domains (3+ years).
I think you are right about link juice. The value of that has increased drastically however these are tweaks and could change at any time but yes, as of this posting it seems that its all about the link juice.
By the way for those who want to learn more about link juice I found a great site to explain it at
http://thekeywordacademy.com/link-juice-explained