The red #16 is definitely a problem with those pinched sections, you will need another #16. You can use 2 screws if you like on the deck for coils. You should have the spring for ease of use, as the airflow screw used as a contact point will turn by itself and cause resistance issues. A cracked glass will most likely leak. The poly carbonate tank is fine except for tank cracker juices.
What brand of clone is this? Was it used?
Considering all the issues you are having, I would suggest picking up one of the Tobeco KFV4's new from a supplier like Elev8vape for $20.
Kayfun V4 Clone by Tobeco
The others here might know were the good deals are, I am in Canada and not up to date on the clearout sales.