^ Sorry, I'm not Asivad, I guess she's too busy celebrating, but maybe I can help.
1. Submit all of them, then list your birth certificate name in the application form under aliases/other names. You can also include an LoE if you want, but it should be OK if you state it in the application form directly.
2. Getting it from your manager is fine, but I also suggest including even a generic certificate of employment from your company, then give an LoE that your company refused to give the detailed descriptions.
3. Recommended.