Can I exceed the pin max output current of a Pro Mini rating by using multiple outputs tied togther to drive a single load?
Only if one output is high and the other low, then they basically short each other and try to drive maximum current.
That is not really recommended but sometime you can get away with it if you can ensure that both outputs will always be at the same logic level.
A better engineering practice is to use a transistor or another driver chip to supply the required current to the load.
Eos:
Can I exceed the pin max output current of a Pro Mini rating by using multiple outputs tied togther to drive a single load?
Not recommended. One pin will tend to dominate and sink more current than the other.
Also, if unintentionally, one pin outputs a HIGH and the other a LOW, it may be smoke time.