To improve the situation abit, try lifting the pump as high as possible. This will reduces head lost also.
Alternatively, u can also rotate yr sump tank 180degree so that the return is pump driectly upwards instead of rerouting the whole distance.
I am using also a 1262 with abt 2.5feet head lost and three elbow, but pump still power full(reckon its abt ~3000L/hr).
Understand yr situation, its a design flaw and u need to live with it(not unless u change the tank so something!)
Cheers