Why am I getting severe hesitation and very poor gas mileage?

There are a few possiblities;

With the bad gas mileage, the O2 sensors could be failing.
The problems with steering and scessories affecting engine would be related to the Idle Air Control valve, which changes parameters dependent on engine load. However, this is at low speed or idle.

Getting a trouble code scan can still bring back codes despite that the CEL is not on. Sensors can be within range as not to trip the CEL but the scanner might catch a code such as fuel pressure, that will shed some light on the problem.

You can check the fuel pressure manually by getting a test gauge. Most Advance autos or large auto parts store chains often have a loaner program for these. There is a test port on the fuel rail.

I think checking the fuel pressure and running a code check, as running a check should be cheap. Scanners can be had for under $100 now, would be the first step.
If the fuel filter has never been changed, that is a suspect.

I will keep an eye on this post for your reply.

The O2 sensors constantly check the air/fuel ratio. This ratio changes as RPM, engine load and other factors change and it follows a mapped curve to optimize the amount of fuel in relation to the timing curve.
This is all done at a stoichenetric value which is where the best fuel economy and best performane values meet.
This keeps things like throttle response, acceleration, engine power when accesories are on, etc. At an optimum level.
This is checked by making sure the aforementioned specifications are met and that as much gas as possible is burnt up in the engine and not wasted coming out through the ezhaust. When this happens, the air/fuel ratio is rich and too much gas is being used. When the O2 senor is hit with the O2 coming out of the exhaust, which should be a minimal value meaning air/fuel ratio is optimal becasue most of the oxygen was used in the compustion chamber. This in turn means the amount of fuel is optimal and the O2 sensor sends a voltage signal to the computer which constantly changes the amount of fuel to keep the air/fuel ratio at the stoichemetric value.
For example, your exhaust has a leak near the O2 sensor, it sees a lot of oxygen so it thinks that the engine needs more gas to use the oxygen up and have the optimal air/fuel ratio. Since the air is, "fooling" the O2 sensor into thinking the engine is running lean, it wastes gas and fuel economy will suffer as well as performance. Other things will happen like backfires out the exhaust.
When the oxygen level is too high, the O2 sensor thinks the engine is running lean as not enough oxygen is being burnt and the lack of fuel can damge valves, etc. So, the O2 sensor sends a voltage signal to the computer to put more gas in the engine by changing fuel injector pulse length, time injector is spraying fuel, or by changing the fuel curve by making it deliver less fuel in relation the the andgle of the throttle poistion sensor. This makes the air/fuel ratio richer in fuel and keeps it at stoichmetric when there is too much air in the ratio.
Perfomance will suffer in the same manner, but the chance for tope end damage is greater. Valves need fuel to stay cool and lubricated or they will, "burn up" and lose their seal to the head and leak.
I the lean situation backfires occur through the intake manifold.
If I put in redundant or you have any questions as I am too tired to read the message, please let me know and I will get back to you ASAP. The O2 sensors constantly check the air/fuel ratio. This ratio changes as RPM, engine load and other factors change and it follows a mapped curve to optimize the amount of fuel in relation to the timing curve.
This is all done at a stoichiometric value which is where the best fuel economy and best performance values meet.
This keeps things like throttle response, acceleration, engine power when accessories are on, etc. At an optimum level.
This is checked by making sure the aforementioned specifications are met and that as much gas as possible is burnt up in the engine and not wasted coming out through the exhaust. When this happens, the air/fuel ratio is rich and too much gas is being used. When the O2 senor is hit with the O2 coming out of the exhaust, which should be a minimal value meaning air/fuel ratio is optimal because most of the oxygen was used in the combustion chamber. This in turn means the amount of fuel is optimal and the O2 sensor sends a voltage signal to the computer which constantly changes the amount of fuel to keep the air/fuel ratio at the stoichiometric value.
For example, your exhaust has a leak near the O2 sensor, it sees a lot of oxygen so it thinks that the engine needs more gas to use the oxygen up and have the optimal air/fuel ratio. Since the air is, "fooling" the O2 sensor into thinking the engine is running lean, it wastes gas and fuel economy will suffer as well as performance. Other things will happen like backfires out the exhaust.
When the oxygen level is too high, the O2 sensor thinks the engine is running lean as not enough oxygen is being burnt and the lack of fuel can damage valves, etc. So, the O2 sensor sends a voltage signal to the computer to put more gas in the engine by changing fuel injector pulse length, time injector is spraying fuel, or by changing the fuel curve by making it deliver less fuel in relation the the angle of the throttle position sensor. This makes the air/fuel ratio richer in fuel and keeps it at stoichiometric when there is too much air in the ratio.
Performance will suffer in the same manner, but the chance for tope end damage is greater. Valves need fuel to stay cool and lubricated or they will, "burn up" and lose their seal to the head and leak.
I the lean situation backfires occur through the intake manifold.
If I put in redundant or you have any questions as I am too tired to read the message, please let me know and I will get back to you ASAP.