I can't answer questions 1 or 2 as I only flew the A320/321 and not the A310 or A300-600, but the answer to question 3 is general airmanship.
In the case of your "small" storm with embedded lightening. I would be inclined to hold off. It's size will be apparent from your weather radar, and you might make an educated guess at it's possible duration. You will also have upper wind readouts from your FMC, this might help you to decide if the storm is remaining static, or whether it might be blown off the approach course.
As other aircraft will probably be making the same decision I would assume that "terminal spot pressure" will be eased. Practically there will probably be mayhem on the ground anyway as the departure rate will also be slowed by the same storm!
Remember of course that a lighthening strike is spectacular but not necessarily dangerous for an aircraft or it's occupants. The fuselage being electrically bonded means it acts as a Faraday cage