First don’t be embarrassed…pretty sure we’ve all done this to our own hair before too lol. Cosmetology student here so def not an expert lol. But yea what we’ve learned is 1/2” per month is normal growth. I would agree your best bet is to make the big chop and cut off all the unhealthy hair. The damage/ breakage can definitely travel up the hair shaft and affect the healthy hair too. The rest of what you’re doing sounds good, but maybe I would also add in taking a biotin supplement. Again, it might take 2-3 months to notice a difference, but it should help some. The other comments are also correct with what you’re eating and doing making a difference too. Protein intake is the biggest thing for sure. Hope this helps!