90 t-bird overheating problems

new rad cap, new thermostat. i've had an endless amount of problems since i had the head gasket replaced 2 years ago. (cost me $700) i haven't had heat since then, and now it's overheating when i drive more than 15 minutes. i learned too late that the water pump should have been replaced at that time...maybe that's the problem...? i had some rad leaks last fall & pumped it full of sealant. it still leaked from somewhere behind the fan (couldn't find the spot...nor could my boss, a ford-freak) but that hasn't happened for a few weeks. it overheats, then when i park & drive ( i don't dare shut the motor off) there is a loud rattling sound when i give it gas.
i may have OD'ed it on sealant, and i'm worried that if i get the system flushed, it will sprout more problems that i can't afford. but...i guess it's better than having to bus it to & from work.
any advice...? please & thank you

The rattling noise when your accelerating is probably spark knock created from the engine running too hot. You really didn't say how much sealant you put into your coolant system, but I do know that using sealant is a temporary fix. You seem to have four choices:
(1) Ride the bus
(2) Repair the car which probably isn't worth it.
(3) Ride the bus and start looking for another vehicle.
(4) Drive the car till it blows up and then ride the bus. if its leaking behind the fan changes are its the waterpump mite be leaking ....the best bet would to get it presser tested to see if u can seethe leak ....is there coolant in the oil or is it smoking white smoke or take the oil cap off and look inside and see what it looks like if its kinds mikly look and see ......and last how doses it run i put in 3 different types of sealant at once. when my rad is low, the reservior is full, and froze up on me a few months ago. i had to add some -40 wiper fluid to get it liquid. could this have created enough of an imbalance in coolant to throw it this far off? could the alcohol in the wiper fluid be a long lasting issue? could there be a blockage to the reservoir due to the overdose of sealant?
unfortunately, bus is not an option where i work.
i know my poor girl is frighteningly close to her end, but i just need her to hold out for 6 more months. there must be something i can do... u should flush it all out ,,,,,,and find the leak and fix it thanks. i'll give that a shot.