Engine life depends on a number of things and is not a solid number. Wear and tear can be going on for compression (even that has several reasons), rods, valves, etc etc. You cannot pin a certain solid number on such a thing as 'life percentage' for an engine. Not by a scantool at least, you will have to measure a number of things and put the info into perspective of original numbers. If you do not have a really urgent need for this, don't do it, really it won't bring you much value.
Most important for a lot of engines is compression status and that you can measure with dedicated tools.