Hi Mary,
Talking up my alley! Been a hairdresser for over 25 yrs, 3rd generation... let's see if I can help.
What it sounds like the colorist did is a process called "highlights/lowlights". Have had it done on me and for me, wasn't my thing. I firmly believe it's in the colorist and technique and nothing more.
1. Ask around to those with highlights that look good (even strangers) and ask where they had their hair done (nothing like word of mouth!)
2. Ask for a free color consult
3. Explain your situation and see how empathetic the colorist is to your situation
4. Explain the desired highlights you have in mind, then have colorist make their recommendations
5. Does the colorist then meld the 2 answers to #4 above?
The colorist has to remember that you see them for a couple of hours... you are the one that has to live with it.
FYI, as you may know... "off the scalp" coloring has no affect on what goes on beyond the dermis layer of the skin. There are reports of "one-process/on scalp" color that does affect since it's penetrates, entering blood stream (since blood vessels sit close to top of scalp).
I have never heard of the "horizontal stripes" that you mention. I sincerely doubt the radio-surgery has anything to do with this result you have been experiencing.
Phyllis