A shahih hadith using the word of a man with such bad memory issues, his own students said not to trust him anymore?

here's a whole lecture on the "memory issues" and "trustability". Do you really think that Hadith collectors would have accepted the Hadith if he suspected the dude wasn't reliable? Good thing we had a western journalist notice while those silly scholars couldn't figure it out for 1400 years.

It replaces his false hadith with math.

Did you actually go through the math and see where the numbers come from? They come from other Hadiths some of which are classed as weak.

So your choices are:

• 6/9 based on a Sahih Hadith which you may have some issues with.
• 19 based on a multitude of Daif hadith which for some reason you're entirely OK with.

Let's take a moment and appreciate the hypocrisy in preferring the second option.

Allah is very hands off about the doings of humans, hence the test part.

If Allah were a teacher he'd be the asshole teacher handing you notes from a student who was in class in 50 years ago, who may or may not have written the material correctly, and tells you to figure it out yourself. If the answer in the notes you got is different than the answer the teacher expects, it's your problem.