You’ll need to fast forward a little, but I present:
Here’s my trick (because I’m happily drunk and feel like sharing stuff), the product of sending thousands and thousands of kittens (Lately I pretend they’re puppies so I don’t feel quite so bad) to their deaths at varying angles and taking notes on my results:
The games bounce physics are actually pretty good, and very deterministic. Your critter loses a little more than half his altitude and some appreciable (but much lesser) portion of his forward velocity every time he hits the ground. Explosives send him up dramatically, but only marginally forward.
So there are two philosophies at work here. The first one is that you want each critter to go very far. You launch them at 45% or so, and they go flying a good long ways. This is a pretty good strategy; I average around 800 with it. Feels good, huh?
Then there’s the other approach: kittens are expendable. It doesn’t matter how many you send to their mewling deaths, because the only ones that matter are the superstars, the ones that go forever. If you want a high score, you’ve gotta think like that. I average down near 200-300, but the ones that get moving go a whole long way.
Here’s the trick: altitude is pretty cheap. You need it, of course, but you get a huge wad of it every time you hit something that blows up, and it roughly doubles every time you hit a trampoline. On the other hand, forward velocity is very expensive, practically irreplaceable.
So we remember our Freshman Physics and Freshmen Economics. We have pretty much constant force. Altitude is free and forward velocity is irreplacable, but we have to spend force to get altitude in the beginning. Pretty stupid trade, huh? What we want to do is have lots of forward velocity and mob the freebies for altitude. How do we get as much forward velocity as possible? That’s right, we launch things in these low, flat trajectories in the blind hope that we hit something nice and explodey while we still have a lot of forward velocity (which is very fast when we have no altitude), since we can then get a lot of distance out of the free stuff.
The rivers are going to run red before your furry artillery shells start getting anywhere. But boy, the ones that do are going to go way out there.
the only thing wrong with your theory is that each time you launch, the obsticles/targets appear in different order and at different intervals
The physics of kitten launching. I smell thesis!
That’s exactly the point. If they appeared in the same places all the time, you could figure out an optimum trajectory and go from there. Thing is, for any given attempt, the optimum is unknown and unknowable, so you launch such that you get the most benefit out of what powerups you get. You only look at the best possible cases, because you can launch as many as you’d like.
I compared 40-degree shots and 10-degree shots.
If you hit a bomb on the first bounce and then nothing ever again, then the 40-degree shot wins by about 120 feet.
If you hit the bomb on the second bounce and then nothing ever again, they’re about equal - the extra altitude the 40-degree shot gets is already cancelled out by the extra forward velocity provided at 10 degrees.
After this, the 10-degree shots win, up until the last few bounces where it tapers out before the 40-degree shot does (if you run out of altitude, you lose). On the other hand, at this point, the 40-degree shot is moving pretty slowly, and even three consecutive bomb hits won’t push it fast enough to clear even 1000 with any reliability.
There aren’t distance markers on the firing range, and early game it’s often hard to even see exactly what’s going on, so I can’t really give hard numbers on the distribution of powerups and traps. Still, I’m getting good results around 15 degrees - enough altitude to hit some of the torpedo-balloons, enough to clear obstacles and survive long enough to hit something good and explosive. After the first major explosive, your initial altitude really doesn’t matter anyhow.
MrJackboots has nearly finished with his, he just needs to sprinkle his last few posts with some greek letters to round it up. 
χχχχηηηηφφφφθθθθλλλλωωωω
Please sprinkle to taste.
More later if I get good results.
Next time I would suggest to your sister that she use the Holy Handgrenade.
Declan