Looking to return to maritime employment – questions for experts

Here is a quick description of my predicament.

I work in the GOM on a supply vessel right out of high school in late 80’s and received my AB limited. I had all intentions on making a career as a captain. I was offered a shore position with a oil company and been with them for over 20 years and currently hold a supervisory/management position.
I still feel at times I should have continued in the maritime industry because it is what I very much enjoyed doing.

questions for the experts:

Is it too late for a mid career change?

Is my old AB license still worth anything or would I have to start all over?

how long would it take to get from deck to a bridge officer for someone who was ambitious?

could my Non-maritime oilfield experience be beneficial in my job search?

in your opinion , which OSV companies would be a good place to start?

Kind regards and Thanks for any advice