hi, what I would do here is first the po126 usually means the thermostat is bad ,and it may be partially open -thus the temp is not reaching what it should in the time frame set by the pcm .
po301 is definately a misfire code for the # ***** cylinder and agreed that with white smoke the plug should be taken out and the cylinder checked for coolant .also, check the spark plug and see if it looks clean or wet .
a coolant pressure tester should also, be used to pressurize the cooling system .and then see if coolant is getting into the cylinder ..
2112 is a throttle body code .I would clean the throttle body ,,for that .
it would be good to take out the other spark plugs and do a compression check ,it is possible that the head gasket is bad and low compression will also, foul the spark plugs and cause a no start ..
if you see no coolant in the cylinders and the compression is up to par --look for around 150-180 in each -if there is a low one or two ,the head gasket or valves may need replacing ..jazzmaster ..