How well does this chemical break down waste and toilet paper? We have a large family and dump once a day. Looking for something that is fast acting.

NOTHING on the market is going to break down TP in one day. I use HP because it's the best I've found hands down. I put in 2 scoops (double dose) after dumping. Then I put in a second dose every 2 days. I dump every 4/5 days I let my tank fill before dumping. We are full time 2 senior adults with a 40 gal tank. A park RV Tech gave me another product I highly recommend with HP. He said RV Shops put a whole bottle in when people have a clogged black tank and let it sit and it Clears blocks about 90% of the time. You can use it for regular daily use in your tan. It's called "Piranha" and it's on Amazon. It's liquid and expensive $25/bottle. God's Speed.

Will this product break down corn?

Ew. This does not paint a pretty picture in my brain, but, since breakfast is now destroyed for me, I will endeavor to answer your...question. I have never seen a stray golden kernel amongst the "loam" as I dump the tanks...so I have to say "yes", it can break down your corn. You may want to get that looked at...btw. Ew...

it says to mix in toilet with 1 gallon of water. has anyone tried addiing 1scoop to a gallon jug of water and shaking the jug then pouring it in tank?

I just drop a scoop in the toilet with whatever water is in it at the time, then hit the foot flush, and immediately dump 2-3 gallons of water from a bucket down the toilet. I've been doing this for 3 years since it was new and never had a problem. It mixes plenty in the bottom of the tank an will mix further every time you flush. Before I move to the next campground or home, I flush the tank, then add a scoop and 2-3 gallons of water and let it slosh around while I'm driving. It will completely clean your tank that way and be ready for the next time. Then I just let it sit that way until the next time I use it. It's sat for months that way and zero odor when I get back in the camper. If it's been siting like that for a while I'll add another scoop when I get to the campground.

Any problems dumping into septic system that could interfere with natural bacteria

I believe it is a natural bacteria...have been using it in our Rv for almost two years and have never had a problem. No odors and it works! One note, when you add it to the toilet, make sure to follow the instructions, i.e. Add the water, then the powder and STIR it until it dissolves.