My central heat and air blower is failing. I don't think that it was blowing hard enough before it started messing up. The air has to run all day long and won't keep up. I can have the control set on 72 and it will be about 77 until the evening once the sun goes down. Same with heat won't keep it warm. I have a coal stoker as a back up when it is really cold but you have to be standing right in front of the vents to really feel it. Most other houses the air coming out of the vents blows a lot harder than my house. I want to put a better fan or speed my fan up. But can't find any thing to help
My house is 1560sq ft with a full basement (3120 sq ft total) basement stays cool all year round about 65

Have you checked the filters? Make sure all ductwork is tight and open. Good insulation? You may be able to increase speed if you have an adjustable pulley or Multi speed motor. Try closing down the basement vents if it is that cold and make sure the basement returns are adequate to recirculate the air