Unfortunately you have been the victim of poor and/or confusing information. This is typical among almost every fishkeeper in the world. We all started out knowing almost nothing and had to learn our through things. Perhaps the most important thing to understand is much ot the information easily found on the internet is more often wrong than right.
Years back for another site I redid their fishless cycling article. I am to old and tired to keep repeating it here and am now also willing to link people to the article. If you want the link shoot me a site PM and I will send the link. The cycling method, if followed to the letter, is failsafe. You will get your tank cycled it is only a question of how much time this takes. There are variable involved over which hobbyists have no control which will determine whether one cycles in 4-5 weeks or 5-6 weeks.
Your problem is caused by what you have done relative to ammonia. Firstly, using fish food or other rotting organic matter is about the worst way to create ammonia in a tank. It will also cause the water to cloud. You have almost no control of either how much is created or when. There are two things to use for this that are perfect. One is pure ammonia and to use this you will need to have an ammonia calculator. These are easy to find online.
I use ammonium chloride. For a single use this is more expensive but easy to use. But I have cycled a lot of tanks and filters over the years and I get the stuff in bulk.
Next, the most common cause of a cycle stalling is too much ammonia. 2-3 ppm is the most one needs. At about 5.6 ppm you will have problems. Most often people do not get that high, but what they do is to keep adding ammonia when they should not. This cause the nitrite to rise too high, and that really crashes the cycle.
Safe Start could have helped but not when the ammonia gets as high as yours did. There are multiples strains of ammonia oxising bacteria. They thrive on different levels of ammonia. The ones we want in our tanks thrive on the lower levels of ammonia created in them. They struggle in higher levels. Bear in mind that the fish (and organic matter decaying) produce ammonia gradually 24/7 and that can accumulate to high levels if not handled. However, when we do a fishless cycle we essentially dump a whole day's worth (or more) of ammonia in all at once.
The bacteria we want reproduce slowly relative to most other type of bacteria. Under the best of conditions it takes the ammonia ones 809 hours to double and the nitrite ones are even slower. The biggest skill one needs to do a fishless cycle is patience. The bacteria are pretty hardy, do not need to be fed every day. The need a few tings beside ammonia/nitrite. These include oxygen, inorganic carbon (CO2 or what is in KH in tanks- carbonates and bicarbonates). They also need some trace stuff which is typically found in most tap water. They will die if the freeze or if the temperature gets too high.
Finally, over time, the amount of the beneficial bacteria there is in a tank will always size up or down to the bioload (all the things that can create ammonia). Add more fish to a tank, more ammonia will be created and the bacteria will sense this and they will reproduce fatsser than they die naturally. Remove a bunch of the fish and the size of the colony will shrink back, it will not reproduce at the normal rate and as some individuals die they will not be replaced. This is not and instant process.
Without going into all the deatails, at this time there are only two products in the USA which contain the actual bacteria that end up in our tanks longer term these are Dr. Tim's One and Only and Tetra Safe Start- they are essentially the same product. They contain the needed nitrite oxidizers wnad the process for detecting them and the bacteria are patented. The patent is shared by Dr. Timothy Hovanec who discovered it all and Marineland for whom her worked at the time. They have parted ways with Dr. H. going independent and Marineland being bough by a conglomerate which also owns Tetra. The bacteria involved are Nitrospira like. other product contained living bacteria contain Nitrobacter which thrives in higher levels of nitrite than found in tanks.
Finally, the nitrfying bacteria in our tanks reproduce by division, they do not form spores. So to obtain the proper bacteria one must be buying a bottle of live bacteria, not spores. The proper bacteria needs to be added to a tank only once to do its job. But you sell more if you can "find" other needs for it, even of they sound good they are usually not needed. There is no need to add bacteria after a water change or because you decided to get a few more tetras to bulk up the group in the tank.
One last note here. One does not need bottled bacteria to jump start a cycle. if you have access to a healthy established tank, there are several ways you can transfer some of the bacteria from that to a new tank. Moving over media, rinsing out media, moving substrate and/or decor all can work. The bacteria in our tanks are not mobile. They live inside a biofilm attached to hard surfaces. The will live in the greatest numbers where what the need is most available. Often, this in inside a filter, but they live all over a tank not just in ones filter.
