Is $720 to replace deck boards, stain deck, and repair pool screen frame a fair price?

I hired a general contractor to replace a few boards on my wood deck, stain it, and fix a loose aluminum frame on my pool screen. The contractor completed the deck and frame repair quickly, but it started raining about an hour after he began staining the deck. He said he'd return for "touchups" the next day. After the second day, he invoiced me for the work, including "stain coat x1", and told me to let the deck dry for 48 hours. Now, the deck looks uneven and patchy, with some cracks between planks not fully stained. When I texted him photos, he claimed it was "absorbed imperfections" and that I only paid for one coat. I'm frustrated because $720 feels like a lot for a half-done job, and I didn't realize the quote for staining would only include one coat. He offered to come back for an additional $350 to apply a second coat. I'm unsure if he's being honest, if one coat should look this bad, or if the rain affected it. I need advice on how to handle this situation and what a good stain job should entail.