A lot depends on context. Brooks is discretionary and what hes showin in his vidoes/books is how to trade in his discretionary way.
Is that a good buy? Ya if you want decent probability. WOuld brooks enter there specifically? IDK, he does like high probability trades so maybe? IDK what he would do, in his course he gives you options depending on what type of person you are.
The 15 bar rule isnt a hard and fast rule because most BOs fail anyway. Considering its a HLMTR (since i cant see the bars to the left) you could probably get away with entering on a bull bar closing on its high. Waiting until the bar you pointed to is fine tho. The more confirmation/higher probability you want or need the less your profit will be, normally speaking. There are of course times you take a high probability trade and end up being in the middle of a big run.
As far as FT. Technically the FT bar is the next bar. HOwever, it can also come a bar or 2 later, at the most. If you have a big bull bar and then a small bear doji, maybe you wait to see what the next bar does since a bear doji isnt a reason to get out. The 3rd bar you reference is a good FT bar.
The bare minimum bulls want in a FT bar is a bull bar, which there is in your pic. Vice Versa for bears. Not the best type of FT bar, but again its the minimum.
NOw if you had that bull BO your arrow is at and then a decent size bear bar closing on its low shows up instead of the bull doji pictured, maybe you think about getting out to reduce risk - since most BOs fail. If the next bar is a bull bar closing on or near its high you can always get back in. If the next bar, after this first bear bar closing on its low, is another decent size bear bar closing, at least, below its midpoint, now you really start thinking about getting out and see what develops.
ETA: damn you have a lot of bullshit on that chart. I just have 1 moving avg that acts as support or resistance. But ya I was right, wedge bottom that went into a HLMTR. Thats pretty textbook. I would have been in much earlier than where your arrow is