hahaha... I just scrounged a 2600gph pump off freecycle. Have no idea what to do with it. Maybe I'll design an amusement park in my backyard with a waterslide. What have I gotten myself into?

Measure the flow by connecting a temporary pipe over the outflow so that it can be diverted into a bucket and time how long it takes to fill it to a known volume. You could also redesign your plumbing. Connect a y or t to the pump outflow directly in the pond and control the flow with your valve at or near the v/t. The extra flow can give the pond extra circulation.

Add an "increaser" to your outflow tube. It should tune down the spraying effect of the water flow. Then you can iopen the valve to get it just right.

rsingley, is "increaser" the actual name of what I need? Is it sold at home depot? Just want to make sure I know what to ask for when I go.

Increaser is not a name. Perhaps the suggestion is to use larger outflow pipe by finding a 1" to 1.5" adapter or coupler. Assuming you are dealing with pvc pipe, they will be available near the pipe.
You could also just shorten the length of your outflow pipe and put a couple of rocks in front to divert and spread out some of the splash and pressure.

It would more properly be called a diverter or splitter.There are a number of adapters available to perform this function.

Diverting part of the flow to another use such as a UV set-up or a spitter or just to send flow into an area without a sufficient current is a good use for a diverter. It is likely to be some distance from the end of the main outlet. Volume of the flow can be static or adjustable depending on the adapter you choose.It is usually a large main tube with a smaller nipple extending from the side.

A splitter usually divides the flow into equal volumes flowing in different directions. It can change a narrow fast waterfall into a wider and slower flow by arrangement of the multiple outlets.The best result is by having the splitter at the end of the main tubing and the tubing from the two outlets from the splitter equal in length so the flow is fairly equal although adjustments can be made to your own liking to allow for such things as different heights, force of the individual flows and flow directions. A splitter is either a T shape or a Y shape.

I don't have any pipes in my set up. I used a black hose (bought at a pond supply store) to run from my pump to the filter. Then another hose to run from the filter to the waterfall. I just have the end of the hose laying in the middle of my waterfall. It's hidden so you can't see it and the water just runs over the rocks. although it isn't the kind of waterfall I was looking for. Maybe I need a splitter for the waterfall too?? Can I get a splitter or divider for hoses? Sorry for all the questions, but I'm completely new at this, not familiar with this kind of stuff, and my husband wants nothing to do with a pond so I'm kind of on my own. :(

Adapters work even better with tubing than with pipe. It is more adaptable.An adapter is rigid and is attached to the flexible tubing with hose clamps. They are great for designing effects for a waterfall. They can go at the end of a tube or in line.To get the tubing over the end of the adapter, stick the end of the tubing in hot water to get it more stretchable. I use a thermos of boiling water.

Don't feel alone for being new. All of us were at one time. I dug my pond all by my lonesome, BTW.

I would suggest that you put a "Y" adapter in the line between the pump and the ball valve that your hubby installed. The pump would connect to one end of the Y (use a short piece of pipe). On the the other end add a short piece of pipe (same as you have now) between the Y and the ball valve. On the final Y connection add a new piece of pipe that runs directly back into the pond. You can control how much water goes to the falls by closing down the ball valve a little. The excess water will exit via the other connection directly into the pond. I have used this method with great success.