97 Ranger
2 wd auto v6 3.0

This is my first time posting and I really need some ideas fast. Thanks.
I bought my fathers 97 Ranger wanting to fix it up since it was mechanically very reliable and has a solid frame, just needed some serious bodywork.

So I have a weekend newspaper delivery route that takes 2 days, covers 300 miles and 2200 papers. So we were going right along good last week and all of a sudden the truck lost alot of power, the check engine light started blinking, started running really rough, and sounded about the same as if the muffler was off.
So after pulling over and realizing it was misfiring I went home changed the spark plugs and spark plug wires. It might of gained a tiny bit of power but ran just as rough. I pulled each wire from the ignition pack and there was a spark jumping to the ignition pack on all 6. So I took it to Advance Auto and checked the check engine light on the computer. It says it is misfiring on cylinders 3, 5, and 6. and o2 sensor #1 is bad. Which I already knew about the o2.
So I had to finish the route as is, it did fine but definitely ran rough. I just ease up whenever the light starts blinking.

So I have only thursday of this week to fix whatever is wrong and don't know where to start or what else it could be. We have only the 1 vehicle running and our newborn in the NICU at the hospital so its getting complicated. I do have a vehicle I can borrow for the first day but need to have it fixed by sunday or drive it like that again.
At this point changing the wiring harness is about all I can think of.
Any idea's whatsoever will be greatly appreciated! Thank you, Teddy Chase

also, it is obviously not the greatest idea, but will I likely do any serious damage if I am forced to deliver again on 3 cylinders?