"probably around 25 lbs. He has tumors. Don't know what kind. He's 11-12. No other problems."

OK, that's what we needed.
Jacks tend to live fast and die too young but lets give this one a few more years of lovin'.

A 150 - 200 pound adult human can tolerate 1 gram of good oil per day.
So, just scale it down.
Start with just a dab and increase it to 1/8th, (125mg.) per day.

Not all buds are equal, and not all extractions have the same concentration, so not all oil is equal.

If the dog fall over or appears distressed, back off a little, then increase more gradually.
Medicine does not have to be unpleasant to be effective.
If he's just a little wobbly when walking, but bright eyed and responsive, you've got it just right.

If the tumors have breached the skin, apply the oil directly as well as orally.
This is a case where you can allow him to lick the lesion, because that activity is healing, and self-limiting.
Mast cell tumors respond quite rapidly, I have no experience with other types.

If his tumors are benign, results are usually less dramatic, but still obvious.

Here's where you can do a solid for dog lovers everywhere.
Start taking pictures, lots of pictures.
Lay a dime, or a quarter next to each visible mass for size comparison.
Then post the sequence of photos here, and elsewhere.
You can tell people about this all day, but, when they see the actual tumor shrinkage, it gets their full attention.

Aloha, and good luck little dog.

Weezard