Boeing says select flap pref 20kts+ below placard speed. Your Capt was correct why did you need F1 at 240 kts?
Descent planning. Keep it simple.
3 times profile plus 1 mile for every 10kts you need to decelerate to 200kts. IE 280kts needs 8 miles decel. 5* GS = ROD required so monitor this if you are not achieving this then you will eventually end up high.
No S/Brake until below transition unless you have really got high or have a tailwind. Panic slowly I say, at FL300 why take S/B when 500 high fighting a 100kt hw, sure enough you'll be pouring on the power down lower.
If you are high within 25nm you need to slow down and get drag out, prior to that you can use speed and parasite drag to assist.
I use VNAV but monitor the profile so I know where I should be at all times. Strong HWind des late and cut into the profile , vv, strong tailwind des. early.