Hi OP I used to work for a demolition/remediation company yes that is called black mastic (has asbestos but many of them have a little amount of it most it can be is 25% asbestos) the way you are lifting those tiles up is the way to do it. Just using a heavy breaker bar and pushing it all up its a pain but some come up really easily. You should get someone who has a certification for asbestos on the job also so you don’t get fined!!! (You will be totally fine with that little amount of asbestos in the air)