Tell us about yourself!
Seems rather odd to use a mains power supply with a third of the power rating of the dc module. Normally one would use double to maximise the output power and efficiency and ensure adequacy. But it is small.
50 watt supply will starve the DC converter if it goes over around 40 to 45 watts. Which will make it unstable.
These flashlights may well be able to produce the 9000 lumens but not for long. They have no active cooling so very rapidly lower the power to keep the temperature down. https://olightworld.com/store/flashlight/x7-maraud... "sensor in real time, and prevents overheating by reducing the output". My Nitecore TM06 has the same type of thermal management, it can output 4000 lumens but only for about 25 seconds. So in reality these units are a gimmick and very expensive.The OP's heatsink could cool a power station!
"34 volt max current"you need to read thishttps://learn.sparkfun.com/tutorials/voltage-curre...
No, 11.1 is the rated voltage, a fully charged cell will be much higher and blow the led