Help!! Need 2013 prius c advice! Death rattle upon cold start up.

Okay I have a 2013 prius C with 172,000 miles. My car just started the death rattle upon cold start up I also have coolant loss. I ran a code scanner and came up with my hv battery is dying and misfire in cylinder 1. I've changed spark plugs on all cylinders and ignition coil pack on cylinder 1. I run my car with the check hybrid system so my car just constantly runs without the ice coming on when at stop signs and red-lights. When I start my car the rattle begins I've learned if you press on the acceleration as soon as you start the car it will stop the rattle after revving up. It started doing the rattle when I would stop at stop lights or stop signs so I took the o ring off the radiator cap and it helped with that it only does the rattle upon cold start up now. I know it's not good to run without a pressuring coolant system but it stopped the rattle during driving around town. I just got a job recently and I haven't had the money to do much like a pressure test or take it to a mechanic. I can't even find a leak on the ground. My oil is not mixing with my coolant and I have no white smoke coming from my exhaust. I've noticed my coolant bubbles and white vapor comes out from the coolant reservoir. I basically start the car step on the gas and after the rattle is gone I drive and it drives normal after that besides having to constantly refill the coolant every 3 to 4 days. I've read egr valves intake manifold head gasket I've researched so much upon the toyota death rattle with everyone saying different things. Does anyone have an idea of what could possibly be the culprit or is my car on its way to the morgue? It's my only car and I'm not mechanically inclined. I drive it 60 miles a Day and it's still kicking. Mpg has also declined. It was running rough till I put high mileage seafoam in the gas tank and that helped with the rough idling. Idk what else to do until I get my first paychecks..