heater core? blown head gasket?

[rmurray31]

so i was letting my lil bro drive car to work i woke up in the morn and there was dried antifreeze all over the engine bay. he said that it overheated and was blowing antifreeze out of the overflow rezivore. he put water in it and drove home (about 10 miles). i checked it out and the water pump belt was broken water pumped looked good and head gasket signs were not there so i replaced belt cleaned it up and got it running again. after awhile now when running (running fine but a little high rpms?) heater is barley any heat a smell almost like brake fluid but sweeter maybe burning antifreeze, white smoke around the alternator area and the blowing through the heater vents, heater off no problem. so what is it and how do i fix it? ty guys