ssh key-pair does not work after I generate a new keypair for AWS EC2 and dJANGO PROJECT

I change the key-pair using RSA 4096 to connect to AWS EC2 through ssh. every thing worked smoothly. however, I could connect using file zella and could NOT connect usinng command line it gives me this error :
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@ WARNING: UNPROTECTED PRIVATE KEY FILE! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for 'id_rsa.pem' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
Load key "id_rsa.pem": bad permissions
ubuntu@15.185.128.193: Permission denied (publickey).
Salehs-MBP:downloads engsalehalomari$ chmod 600 id_rsa.pem
Salehs-MBP:downloads engsalehalomari$ ssh -i id_rsa.pem ubuntu@15.185.128.193
Load key "id_rsa.pem": invalid format
ubuntu@15.185.128.193: Permission denied (publickey).
Salehs-MBP:downloads engsalehalomari$ chmod 600 newKey.pem
Salehs-MBP:downloads engsalehalomari$ ssh -i newKey.pem ubuntu@15.185.128.193
Load key "newKey.pem": invalid format
ubuntu@15.185.128.193: Permission denied (publickey).

I tried all possible solution on stackover flow but nothing worked

I need some one expert in AWS EC2 and Django
the second issue Before I changed the keypair, the apache2 server was working so good but when II changed DEBUG=FALSE in DJANGO SETTING, the server shout down

any help to solve these 2 issues