Calculate Average time and then working out difference between times

Morning all,

I am new to Power BI and I am already converted to it!

I am working with a data set (below). The first column is a reference number, the second is the time that process started, then the next are time stamps along that process flow. Each column represents a different step in that flow. There can be multiple flows for each reference number as you can see below. Sometimes a step is also missed out

I am trying to show 1) The average time taken between columns 2&3 (however want to exclude some high value numbers that will throw the stats out. I then want to show an average time difference between each step in the process, again ignoring the high value items which will push the average up.

Finally I am looking to produce a bar graph of column B which will show hours across the day when they start, which will show the busiest hours.

Any help would be appreciated.

Thanks