Half-circumference damage shouldn't be fatal. You may need a fancier, padded support. I have two males, as relying on one of anything in gardening is risky.

The one-to-several ratio is for orchard grids. A short row may be better served by two males near the ends in case the wind during pollination comes from one prevailing direction.

I wouldn't worry about your set-up unless it doesn't produce well in the future. Seaberry fruits on 3 and 4 year-old wood.

Seaberry has tendency to have a lot of suckers. They are easy to propagate by cuttings too. If you afraid that tree will not survive, just root a few cuttings from this tree (to be sure, it's male ) or separate a few suckers.