In the canon, Watson was consulted on cases after Holmes' death. And he did seek out cases to be solved, that was how he bumped into the disguised Holmes.
I'm not sure why you think the mafia are after him & think he is Sherlock. That was a mistake by one person in the second episode. No evidence that anyone else thinks this at all.
Would he? He may try but the man is suffering from PTSD he won't want to do too much in that line of work I am sure.
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Also, please note that sentences can also end in full stops. The exclamation mark can be overused.
Sherlock Holmes 28 March 13:08
Mycroft’s popularity doesn’t surprise me at all. He is, after all, incredibly beautiful, clever and well-dressed. And beautiful. Did I mention that?
--Mark Gatiss
"I know that you believe you understand what you think I said, but I’m not sure you realize that what you heard is not what I meant."
Robert McCloskey