Hi there and welcome!
That is a good job for a 1st attempt on a brisket!
I think you discovered a lot of good lessons learned.
Also I noticed that you put the meat probe in the point. The point is hard to mess up, hits temp and gets tender waaaaaay before the flat does. That flat is the problem child. Next brisket try putting the meat probe in the thickest yet center most portion of the flat (usually in the area where the flat and point come together). Be careful to keep the probe in the flat muscle and not in-between the flat and the point where there is a layer of fat.
If you are worried about drying out some of the brisket buy ones that are 15 pounds or heavier (if the wallet can handle that) and trim the thin portion of the flat away like this image suggests:
Repurpose that good carved away meat so it gets put to good use. I have some options posted here since I do the same thing https://www.smokingmeatforums.com/threads/my-brisket-flat-trimming-approach-explained-qview.286564/
The easiest thing to do with that meat (in my opinion) is to just throw the chunk of meat in with the brisket and pull the chunk when it is done rather than letting it cook the whole time with the rest of the brisket and becoming crusted up trash can fodder. If you don't carve that piece away it often becomes crusted trash while on the brisket anyhow, hence the recommendation to carve and repurpose it :)
If you pull it early or take an approach like the one in that link I posted you can end up with more good brisket meat :)
I think you learned that you can trick yourself while probing for tenderness. Simply stab all over INCLUDING the thickest yet center most portion of the flat and when it is tender ALL OVER then you know it is done. That thick center most portion of the flat (in the middle of the whole brisket) is usually the last to go so don't avoid checking it for tenderness lol.
Finally, be prepared to learn something new each time you cook a brisket. There are always areas to tweak and improve upon. Whether it is trimming, seasoning, smoke wood parings, wrapped (foil or butcher paper), going naked (my preference vs foil wrapped, never paper wrapped myself), smoker arrangement for loading/unloading the meat, slicing approaches, holding approaches, smoking temp preferences (I prefer 275F), etc. etc. etc.
Enjoy it and welcome to the world of brisket!