Lord_o_o_Spoon definitely provided some good points. However, there were also a lot of questionable/incorrect comments so you need to take them with a large dose of salt.
I tried to answer the three questions you had, but I don’t think any of those were the actual key moves - you played fine for both move 7 and 143 (the issue with the latter is due to a slack move at 139). Move 19 was slightly suboptimal but not super impactful.
The moves you should re-examine include 27 (too soon to play on 1st line except when you need to), 53 (corner is hurt when white play R7 naturally), 73 (why not D5 and keep white separated while keeping yourself strong), 89 (can you find more efficient ways to protect the push), 91 (not necessarily bad, but you need to have a plan when you play contact moves like that - the game result was quite bad), 117 (trying too hard and in fact helps white get stronger - same issue as some of your peeps), 127 (again, helps white get stronger, a “thank you” move), 137 (same issue), 149 (can you see what happens if you play K18 instead), 151 (hurts your group at L3), 173 (not needed), 175 (not needed), (skip a few moves that are questionable but not super bad), 209 (why not just capture the stones at L8) 229 (there is a snapback at P5 worth 30+ points), and 259 (what if white cuts at C15).
When you resigned, I think you could have won the game by playing P5. There is a later follow-up at L8 so even if white cuts at C15 you should still have enough points.
Let me know if you have any further questions! @mister10