I would trust the plane, though only two engines might be a problem if one fails.. but the low fuel consumption has to come from somewhere.
Trust the airline? I think yes. I suppose the missing plane was either hijacked ot the pilot suicidal. Singapore airlines has had not much losses otherwise.
Airbus industries is aggressively trying to get a big share in the world's markets, and also within the US of course. But since good old capitalism and greed are still seen as the main motive in life and development, they should not complain too much
Regarding only flying Boeings.. Boeing is meanwhile also controlled by electrical steering and electronic controls, from the effort of quality control Boeing and Airbus are equal. Problem is apart from the manufacturer's control and airframe invention and building, that each airline company can order its planes with an own configuration, from jet engines to computers, to black boxes, backup systems and so on. A Boeing can have Pratt&Whitney, MTU, Rolls Royce or whatever engines. Controls and computers can be ordered by other companies than the plane manufacturer.
Countries or national airlines can also sometimes demand wing profiles and details when it comes to big deals, so parts can be copied.. with
varying results.
Also, maintenance is ordered by the airline(s), not the manufacturer. The latter can give recommendations and advice, but...
Aftermarket spare parts are often of lesser quality, and produced in China with "original" manufacturer's numbers, and logo
Crichton's
'Airframe' is a very good book on that matter, still today.