Are non-germinating peas alive or dead since they can't reproduce?

Answer 1

They are not viable so are not capable of living. They entered the lag phase to await suitable conditions and either lost too much water or germination inhibitors were to concentrated producing a loss of viability

Germinating seeds retain water sufficient to allow germination after the dormant lag phase. This implies their membrane system integrity is unimpaired.
In phase I of hydration all seeds have bound, bulk and free water. During the lag phase (phase II) of hydration the non-germinating seeds loose their bulk water component but germinating seeds retain their bulk water so remain viable.
Pase III is the rapid re-hydration once conditions allow. Viable seeds take up water and re-organize internally with an increase in bulk and free water but a decrease in bound water.