1. What is the approximate or average time from invention to
publication (for example in 1895 a paper could be published in 5 days
- the discovery of x-ray for example - in the 1950's - the discovery
of DNA - 52 days). Nowadays, due to journal rejection rates and other
factors, it can take 2 - 3 years for a discovery to be published. I
would like a reliable figure and a source.

I dont need many sources for the answer. As long as there are a couple
which provide the answer and are RELIABLE and QUOTABLE, that is
sufficient.

There is no reliable answer to this question.  Many inventions are
never published in a journal.  Subject matter and journal make a huge
difference as well.