So here is my thought and opinion.
So I have to scold you here like it or not.
Do not add sacrificial fish for entertainment that's just cruel.
If you don't respect the lives of the fish well maybe this is not the hobby for you.
I hope that was a joke or sarcastic statement, and not a real thought.
It will not teach your children to respect life if you do not.
Ok scolding over.
So you overdosed the ammonia ok. you should have simply done a 50% water change to reduce the overdose and let it alone. That time has passed and your on to what you have today.
With the addition of Seachem Stability your changing the ammonia and not allowing the beneficial bacteria to do the job like it is supposed to do. Thus defeating the goal.
This product is primarily used for a livestock filled tank and you have ammonia issue arise, and you have to act fast.
It does the job of the bacteria that is not doing the proper job for whatever reason.
I don't know what Bacter-Gen MD is, or will do for you. This is the first I have heard of this product so I have no idea if its good or bad.
I took a look and I see this is your introduction of beneficial bacteria to the system.
So IMO if your having a second ammonia spike then the bacteria is or has not grown, and may be dyeing off. Thus creating a spike.
As you have not added anything for two weeks are you sure nothing was introduced without your knowledge?
I recommend buying a bottle of Dr Tims one and only, or BioSpira and adding this to the tank, nothing more. No water changes nothing for the next two weeks.
Then test foe ammonia and Nitrate. it should be Ammonia 0 and Nitrate 20ish more or less.
Do a 60% water change wait 24 hours and test again. If Nitrate is down then you may be able to add a fish.
While your waiting please research the nitrogen cycle information here on reef2reef.
There are comprehensive threads that will explain the nitrogen cycle and what its about.
Click Here