blue smoke on start up is usually vale seals that are worn out allowing oil into the cylinders after a long sitting time.
after many miles, the bearings wear and will lower the oil pressure. change viscosity of your oil and it will hold the oil pressure a lot better.
coolant leak is something you need to deal with now. have a shop add dye to the system to determine the leak. the low coolant level could be the reason for the heater not working all the time too. do not use sealer as this will clog the heater core and not fix anything.
Roy