It might not be required but thats not for your convenience, get test before coming or you might get stung for 100,000 plus Baht per person that your insurance company will refuse to pay.
If you don't have the correct information the visa company will still take your money and you still will not have a visa, the most important thing you can have is g/f work history present employer with letter saying she allowed time to go USA and she will be returning, if you don't have that don't waste your money.
Only itching because you scratch it, when you get a bite just control yourself from scratching and in about 20 minutes it's stops, but once you start scratching it can itch for 1 or 2 days.