I would just use AQ salt. It doesn't look bad to me. The AQ salt might clear it up in a matter of days.
I think most tests on five gallon tanks reveal that ammonia shows up after about 5 days. As long as you are testing daily and doing a change any time you see ammonia/nitrites, he should be fine. Personally, I don't test for nitrates more often than once a week because it won't build up to toxic levels sooner than that. If you have a liquid test kit, the nitrate test takes the longest :p
Also, I did daily partial water changes with AQ salt. Most people will recommend you do. If you have 1tsp per gallon and you do a 20% change, you will remove 1tsp and therefore will only need to add 1tsp (does that make sense?). When you are finished with treatment, you will need some large water changes to remove the salt. Two 50% changes would still leave you with 25% of the salt left.
I have two 5 gallons myself and have done salt treatments in the whole tanks several times (with epsoms). I just take a cup of tank water, add 5tsps of salt to it, stir it up until its all dissolved and then add a little bit at a time an let the filter mix it up. Sometimes I will use a skewer to stir the water a bit.
The salt will change your pH so that's why you need to add it and remove it slowly.