Sodium hypochlorite is bleach so unless there is something else mixed in with that, what you have is just strong bleach. (Regular household bleach is just 6% sodium hypochlorite). So, unless there is some other gunk in there, (which I doubt but you better look at the ingredients to be sure), then it should be fine to use.
If your chlorine is much higher than 5, your pH test may be inaccurate. High chlorine causes falsely high pH readings. Until you buy the good kit, you can use a dilution method to make your test kit read higher. More about that here: Testing Without a Good Kit
The test kit you want to get is the Taylor K-2006 or 2006C which you can get from the testkit link in my signature below. It is the best one out there. You cannot buy it locally, however.
Hope this helps! Welcome to the Pool Forum!
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