Re: ceiling swing
First let me apologize for your first contact being our resident Googleist who has failed to provide any credentials at all.
The 2X4 is not strong enough, especially considering the shock loads it may be subject to. Depending on the width of the room, you could have steel or larger wood cross member installed . Considering the lumber currently available, I wouldn't want my livelihood dependent on marginal at best. Considering the liability involved, I would suggest you get a contractor who knows what he is doing to do the installation.
Be sure you live your life, because you are a long time dead.-Scottish Proverb