does anyone know if it's rare to have 8 DNA variations on one gene?
Yes it can happen, most variations will not have any clinical significance.
a single gene contains hundreds or thousands snp, so you are likely to have many variations;
The more 23andme will give you snp in a gene, the more you will find variations.
So you have to target and screen what you are looking for, and Enlis is a powerful tool to do it.
Here the way you can screen the ETFB gene via Enlis.
First you will open the window "gene category or gene list" like below you choose "gene symbol" and write the name of the gene you are looking for, and then you click on the "go" button:
You can see my variations are all on INTRON and with a allele frequency above 30 %
So they are unlikely to cause any problem.
If you want a better screening, you will open two other windows:
"allele frequency" (choose 1 or 2% for example)
"protein impact" (you can choose everything in this window)
Then you click on "go" button, and you will see nothing relevant is showing up anymore: