Wow, first off, is there anything un-opened that you can return and get your money back???
ok, the next thing to do is unfortunetly spend some money...get the TF-100 test kit, will be around $70 i think. we really cant recommend anything without first knowing your levels. remember, we arent the pool store and are not just going to say to buy a bunch of stuff to fix your pool without knowing exactly what to fix. and no worries, we are going to save you enough money to make up for that $250 mistake.
you said it was a new pool, where is the pool builder? they typically take care of the startup and we try not to recommend you do anything until they "turn over the pool" to you to avoid any issues with voiding warranties.
its odd that your pH is so low, being that a new concrete pool should have high pH, my guess is you have added too much acid...2 gallons seems like way too much. i would just run the pool and see if the pH comes up by itself in the next couple of days. if its still low in a day or two, we can adjust that up.
Right now, all you can do is try and keep your chlorine up. use regular old bleach, 8.25% to increase your FC. Add enough each day to add 3ppm. you said it doesnt matter that you are at 0.5ppm, but really thats the most important thing. i would try and keep your chlorine above 2ppm at all times, last thing you need to deal with is an algae breakout. once you get the test kit and know your CYA levels, then we will know your required FC (free chlorine level).
once you get your TF-100 test kit we can figure out where to go. last thing we want to do is add more of anything with not knowing the situation.
and by the way....WELCOME to TFP!
one last thing...time to read up! go read all the links in the pool school tab at the top of the page