Hi zent1000,
It sounds like your father is living a happy, healthy life
Having counts at the low end of normal is not a concern. The ranges are statistically based. Normal is normal.
A slightly elevated MCH is probably okay, given that everything else is normal.
B12 is usually obtained in the diet through dairy and meat. As a person ages, their ability to absorb B12 from food decreases. So, if your elderly father is a strict vegetarian, it probably make sense to continue the B12 injections. Excess B12 is eliminated through the urine.
I am not a doctor but don't think your father needs extra tests at this time. I can imagine that it is hard to manage his health from so far away, but it sounds like he is doing well!