Things are definitely looking up. Looks like you caught the rot before it got too far, which is essential- and not easy to do, so props for that!
Start with a low EC and bring it up slowly, so your roots can handle it.
Be certain all the H2O2 is out of the system before addig any beneficial microbes, as the H2O2 will kill all microbes indiscriminately.
Remember that the colder your water is, the MORE dissolved oxygen it can hold in solution. This is good for beneficials and bad for rot, slime and pythium. Keep your res. temps where they are, or even a bit lower. Won't hurt a thing. I actually run mine at 64 with good results.
And one more thing; don't put the molasses or any other microbe food in the hydro water- it will feed everything in there, which could well include the nasty microbes you're trying to get rid of!