For tomatoes the pollen is sensitive to high temperatures. In summer many tomatoes become male sterile.

I would suggest your ability to make crosses would be improved in greenhouse chambers where lighting and temperature are controlled.

Pollen can be affected by nutrition and complete plant analysis can be combined with drip line and foliar application to optimize the nutrition compared literature values.

Spray with zinc and Boron at flowering stage

To maintain a high quality pollen in anthers of a flower we must supply the required nutrients and supplements along with water. avoid plant to stress at maturity either salt, heat,or water stress. high temperatures may lead to drying of pollen and when exposed it becomes sterile.

Pests and their treatment options are both problematic. Thrips eat pollen, but some sprays used to control them can also cause temporary loss of pollen viability.