Canned/tinned anchovies are salty!

Ref canning: You put hot stuff in hot jars, clean the lip/rim of the jar, put in warm to hot water. The pressure canner raises the boiling point of both the stuff in the jars and the water in the canner. This forces the air out of the jars (under the rubber rim of the lid flat and around the screw part ring of the lid.

Thus, when the super heated jars cool, it creates a vacum. It also cooks whatever is IN the jars even more. This is why we use raw veg and fruit.

For this sauce, I'd leave a 1" air/head space in the jars. When this stuff boils, it will burp...and if not enough head space is left the sauce will burp into the space between the rubber on the flat and the rim of the glass jar and not seal.