SQL Services Wont Start After Removing TLS
You have to patch the sql server instance to a newer version to be able to use TLS 1.2 

Take a look at TLS 1.2 support for Microsoft SQL Server

Either patch at least to SP2 CU10 (preferably a higher CU)
 or SP3 CU1. 

When patching to SP3 CU1

You would still be 9 CU updates behind, the latest CU for SP3 at the time of writing is SP3 CU10.

So when going this route I would go for SP3 CU10 but preferably choose for SP4


  Note: TLS 1.2 support is also available in 2012 SP4.


When patching to SP4 (preferred)

In short, simply patching to SP4 would be the preferred option, you have to remember that there is a hotfix out for this Service Pack. 

More questions and answers on disabling tls 1.0 and the sql server service not being able to start 
here and here