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YES! The following article has a lot of information on this subject:
https://www.gardeningknowhow.com/composting/ingredients/coffee-grounds-gardening.htm
You can also enter coffee grounds or tea leaves into the search window to get to more atricles on this subject.

Ammonium phosphate is used as an ingredient in some fertilizers as a source of nitrogen. It is also used as a flame retardant in thermoplastic compositions. It is also used in bread making to promote the growth of the yeast.
After entering "ammonium phosphate fertilizer formula" in a search engine, 146,000 results were listed.

This article should answer your questions: https://www.gardeningknowhow.com/composting/ingredients/coffee-grounds-gardening.htm

I would recommend adding it in the spring. Adding it in the fall can cause plants to grow at the end of the season rather than go dormant and, in empty beds, it could wash away some since there are no plants to take it up.

While an abundance of potassium is usually not toxic to plants, too much potassium can inhibit the absorption of other nutrients, which may lead to the nutrient deficiency. The signs of which depends on the type of nutrient the plant is lacking, but includes stunted growth and yellowing of the plant. Here is more info: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/plants-potassium.htm

Rather than trying to mix, I would just go with the 10-52-10. Too much fertilizer can harm a plant as much as too little. Instead, try adding some potash for the extra potassium and leave it at that. Guidelines for fertilizer are just that, guidelines. So if you are close to the mix they recommend, you will be fine. If you have not done so already, I would get your soil tested. This will tell you more about what your soil needs and lacks, and you can adjust that according to your plants' needs. Here is more info on that: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm