Q: No pickup power, shifting gear problems, hose loose

"Last week my car started running terribly. Normally it has very good pickup, but not now. Then shifting gears became difficult. It revs to 3 or 3.5k RPMs, then won’t do anything at all! The RPMs don’t go higher, nor faster and sometimes it won’t shift and then I have to let go of the gas or it shifts. Today, it was even worse so I looked under the hood and saw that the air intake hose between the filter and engine block was disconnected. After putting the hose back into place, it was a little bit better, but my car still runs badly! I think it has 140 hp, but it feels like only 60 hp. For more details: I’ve kept up with oil & filter changes, air filter replaced recently, fuel filter and trans fluid have ‘not’ been changed but fluids are always topped up. My car is always locked, so no one has messed with it. The o clamp was very loose and the pipe and air filter housing slipped apart and now the transmission is messed up. When I disconnected the positive power to see if it was a sensor, that was fine. I’m thinking I might need to flush the engine or do you think it’s more serious than that?"