I doubt the tip not being flattened is an issue. I know I have done a couple without flattening it. I am also super critical about the belly being parallel to the back. My TDs are within .001 either way, meaning I will leave mine tapered the wrong direction if it's within .001 or the right direction within .001.
Taper from side to side is no big thing... infact if it is too parallel, they can be a sumbit to pull apart. I do try to keep them somewhat close.
In all these years and over 1200 + TD's, I can honestly say that I have never re cast one because of fit, but I have had two failures this year.. both bows were over 8 years old. One was a 57 lb... I believe 11 years old and around my first TD I ever built. I did not put enough reinforcement in the riser. I don't remember doing it, but all it had was two strips of clear fiberglass used like an I-beam. The other, I over ground. I didn't use the carbon strip inside so I could tell how deep my grind was.
If you watched my TD videos, I have quit using the tooth pics and no longer do the miter cut with the table saw.
I now just cut it in two with a bandsaw and align them back up by eye. Another thing I did that has made sanding the tenon parallel much easier was to get a block wider than my tenon and apply sandpaper to it. I use paper with self adhering tape so it can be easily replaced. This eliminates the possibility of making the tenon hour glass shaped.
Good luck, BigJim