can be used any time within 6 months from that date of issue
I'd double-check the "use by" date - ask the closest Thai embassy or Consul. Recent tourist visas I've seen have to be used (for the first entry) within 90 days of issue.
I agree that real tourist visa would be better. No need to change money to pay the fee before the VoA channel, no need to queue twice, no issues re: boarding (not that there would be as long as you meet the requirements).
Sorry I missed the September travel date. Agree it's 50-50 that they extend these lower prices again, and they might not decide until 28 August.