How to "start" the sequence/s?

There is no reason to create a sequence library. Just create the sequence you want to start, then start it.

There is no reason to raise/drop objections on every sequence if your test does it for you and the sequence blocks until it is done. It’s extra overhead.

There is no reason to be using legacy OVM global_stop_request() as it has been deprecated. Dropping the objection will end the run_phase.