I have a concrete block foundation - house built in 1948. When we bought it 34 years ago, there were some vertical cracks in the front foundation in the basement. When it rained hard, or we watered the front foundation shubbery, it leaked like a sieve.

My husband spend an entire summer digging out the foundation in front and applying tar. He then also put in 2-3 ft of gravel in the bottom, then the soil and this time, he made sure it was banked AWAY from the house. In the basement itself, he used some special product - have no idea what it was - and filled the cracks.

We have had no further leaks in the foundation, thankfully. Most cracks like this are caused by settling. This was a well-built house - a rather expensive "starter home" in it's day.

It appears you are concerned about the structural capacity of the foundation rather than waterproofing but I'll take up both.

Waterproofing - To waterproof porous CMU ("concrete masonry unit" is the generic construction industry term — "cinder block" is light-weight CMU made with fly ash) requires an elastomeric (flexible) membrane like spray-applied modified (rubberized) asphalt applied to the outside of the wall and protected with a rigid fiberglass or polystyrene board. A footing drain completes the waterproofing system. Tar is not flexible and is considered dampproofing rather than waterproofing. I didn't know it was still sold.

CMU construction - It is common to reinforce CMU with horizontal metal "ladders" in the joints. When the unbalanced fill (distance between the slab and the exterior grade) is greater than 3 ft, vertical rebars are placed in some of the CMU cores and the cores are filled with grout (not mortar of concrete). A mason might know if there is way to find them,

Cracks - A vertical crack may be from exterior soil pressure especially if water is allowed to drain against it or a car parked there but a diagonal crack indicates a footing that has settled which often occurs at a corner.

I can't say if the repair is a good one without more information or a photograph. You will eventually need to get a good mason to look at it so you might as well go ahead and call one.