Re: reduce their payrolls so that
In my opinion, the semi-colon is not proper there. I'd used an em-dash, and I'd say "to reduce" instead of just "reduce."
It's made more awkward by the repetition of the word "reduce" in the in the beginning of the next sentence.
It would look overly fussy with a comma before "so that" since the parenthetical phrase "if they can maintain their sales revenue" is also set off by commas.
You seem very interested in semi-colons. Really, they aren't that common. I use them only when two independent clauses are so closely related that it seems odd to make them separate sentences (rare) and to separate items in a list when individual items have commas within them (even more rare).
The over-use of semi-colons will make your writing look unnatural.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.