This is a complex problem, and it's going to be difficult to provide an accurate answer without inspecting the equipment. So this is going to be more like a few comments, than an actual answer.
Water heater
I'll start with the water heater.
Old units aren't efficient
If the unit is older, it's likely not performing at peek efficiency, which is wasting energy. Updating the unit could save you money in the long run.
Tank heaters waste energy
No matter how much hot water you use, the heater is turning on from time to time to heat the water in the tank. The only way to eliminate this waste, is to install an on-demand unit.
Fuel source cost
Depending on the costs of different fuels in your area, switching fuel source could save money. Installing a gas fired on-demand water heater, could save you money long term.
Fireplace
If the fireplace doesn't have a fan, that is blowing heat into the home. You're quite possibly drawing more cold air into the home, than the amount of air the fireplace is heating. By using the fireplace, you could be blowing money out the chimney.
Also, the cost of wood is typically quite high, compared to other fuel sources.
Heat pump
Heat pumps use a lot of electricity, which in many parts of the country is an expensive fuel source. In temperate climates, heat pumps make sense because they're not typically used much. In climates where the temperatures often drop below freezing, heat pumps are virtually unheard of. This is because heat pumps aren't so good at heating homes, and often have to rely on supplementary electric heating elements.
Use the furnace on cold days
Since you have a gas furnace in the home, you can use that when the heat pump can't keep up. Depending on the local gas price, this could save you some money. In most dual fuel systems (like yours), if the heat pump can't keep up it shuts down and the furnace runs instead.
From your description, it sounds like the furnace and heat pump are running at the same time. This is not a good idea, and can actually cause damage to the system.
You'll want to configure the system (or have it configured) so that when the thermostat switches to auxiliary heat, the heat pump shuts down and the furnace kicks in.
Without actually being at your home, it's difficult to diagnose the problem. You might want to have an HVAC technician come out and evaluate the system, to help determine if you're wasting money.
Best Answer
There are a couple of ways.
Are you comfortable when it's really hot or cold outside? If so, then it's sufficient.
Do a Manual J heat load calculation. You can do a crude approximation of this yourself using http://www.loadcalc.net/
Use "rules of thumb." These rules depend heavily on your area and become less accurate the better or worse your house's thermal envelope is.
You have a roughly 3,000 square foot house, assuming the basement isn't insulated/sealed off from the first floor. And you have a 30,000 BTU heat pump. That means the primary HVAC system can provide 10 BTUs per square foot. If you house is average to below-average construction in terms of insulation and air-tightness, this would most likely be insufficient in Minnesota, Maine, or Montana. But it would be probably be fine in California, Florida, or Georgia. In the middle third of the country, it might be okay, might not be. Might depend on how cold it got.
The fact that you have a (relatively) low BTU central ducted heat pump coupled with an electric furnace tells me that you live in a cold climate, and that the people who installed this system suspected that the heat pump would occasionally not keep up during cold snaps, and added the electric furnace for back-up. It woulda been a heck of a lot cheaper to simply calculate the load correctly and install a right-sized heat pump in the first place...
Another thing to consider is that a lot of older heat pumps don't work very well below certain temperatures. So if it gets to be -10 outside, the heat pump might be incapable of producing any heat. Newer better Japanese heat pumps can manage this without electric, gas, or wood backup heat, but most older American ones can't. So if it gets really cold, you might be forced to rely on the electric furnace, which will cost you big bucks to run.
I would highly suggest you improve your house's insulation and air sealing. After all of that, you might discover that your heat pump works just fine to heat and cool the house.