Meaning of さすれば as a verb

Question

In the passage,

この救済の光を
さすればここは幸福な場所となる

what is the meaning of さすれば? Is it the kana for 然すれば?

In this context, I would have expected 射せば to be written instead.

Answer 1

さすれば is そうすれば (="if you do so", "then") said in an archaic fashion. And yes, さ here is 然, an archaic word that means そう in modern Japanese. This さ is almost dead now, but is found in a few set phrases like さも, さもありなん in modern Japanese.

(光を)射せば happens to make sense in this context, but it's not relevant.