While being careful and following procedure for fueling, starting, etc the Atomic 4, there is no reason to be paranoid. Regarding fueling, where is the fuel port on your boat? It should be located where no fumes can travel down into the bilge and probably is so situated. When I purchased my 1976 Atomic 4 equipped boat I replaced the entire fuel system, tank, lines filters etc and check them regularly for any signs if failure/leaks. Always use the blower for 5 minutes before starting (and I run mine for a few minutes after stopping) the engine.
What is nice about the Atomic 4 over diesels is they are much quieter and they don't smell so much. In a small boat, the diesel smell can permeate the entire cabin and it is very hard to get rid of it. Also, gasoline engines are much more suited to the short run times typical of most sailboats than are diesels.
The "bomb" appellation is totally undeserved. Boat fires are caused by several reasons, cooking fuel, bad electrical wiring, engine fuel, etc., so one has to be fire concious all the time. Just this week a shrimper caught fire in our marina and burned to the waterline diesel engine and all.
Enjoy your boat and your Atomic 4 and if you ever have to replace it look at the new diesels as they are much better engines than they were back in 1978.