There's some things you should know about TPS settings. First, the normal range is .9 - 1.0 volts at idle, with about .98 being pretty typical. 4.64 volts at WOT is very common. Anything above 4.8 would probably trigger a bad TPS code. Same for anything less than .9.
There are 3 modes that the PCM categorizes the TPS position. Idle, part-throttle, and WOT. Idle is pretty much zero movement of the TPS. Part throttle is anything about .02 volts above idle and up, until you get to WOT. WOT is usually around 65 - 70% of the way to the floor. Despite the pedal not actually being totally floored, the PCM still sees these heavy throttle positions as WOT, because at that much throttle, the PCM is going open loop and commanding enrichment the same as it does at WOT anyway.
Setting the TPS idle is the most misunderstood part of the equation. First of all, TPS's are not adjustable. Some of them do have one of the two screw holes enlarged, which does actually provide a hair of "adjustment" room, but in all reality, Ford just enlarged that 2nd hole so that the screws were easy to put in, and the thing didn't have to be aligned perfectly. Some people, in certain circumstances, do enlarge the holes to make their TPS adjustable. This is only necessary when you need to jack up your minimum airflow screw (the throttle body stop screw) higher than stock, which puts the TPS too high, requiring TPS modification. It's doubtful you'll ever need to do this, unless you have a heavily modified engine.
The way the PCM determines what is idle and what is part throttle is a floating way, which is what's usually most misunderstood. When you turn the key to the ON position, the PCM reads the TPS voltage. Lets say yours is .98. The computer now stores that .98v as "idle", and anything .02 volts over that would engage part-throttle mode. So if your TPS idles at .93 volts, then .95v would be your part throttle. See how this varies? That works, right up until about 1.1v, where you're just flat getting out of the range of what the computer would ever see as idle. So if you have to modify your throttle body stop screw way up for some engine mod, you might have to modify the TPS to get it back down below 1.1v. But quite frankly, your tuner should be tuning the idle tables for larger cams and such.
The engine should just barely be able to breathe, with the IAC disconnected. When you unplug the IAC, it closes completely, so the engine would now breathe just thru the throttle body air gap. Most of the time, this minimum airflow screw should be set to where the car just barely stalls when you unplug the IAC, or at the most, so the engine just barely runs with it unplugged.
From there, the IAC adds some air (15 - 30%) to control idle up to normal idle speed. Then it adds another 15% or so to compensate for the A/C being turned on. Then it adds even more percentage of airflow to get the engine to idle fast when cold. As you can see, this extra airflow required by the IAC adds up to more and more duty cycle in a worst case scenario. The job of the minimum airflow screw is to add the minimum amount of air the engine itself will need to run, and the IAC picks it up from there and brings it to the desired idle speed.
In short, you should never have to mess with the minimum airflow screw. But if you have a modified motor, or feel it's been misadjusted already, then unplug the IAC and set the engine RPM so the engine either barely barely runs, or just stalls out. Then plug in the IAC and check the TPS voltage, to make sure it's in the .95 - 1.03 range, with .98 being your target.
A backwards method on a bone stock car might be to adjust the minimum airflow screw until your TPS says .98v. I have seen plenty of vehicles in that low 1.00 - 1.03 range, so if you're there, call it a day. Ford probably calls 1.0v it.
The TPS has several jobs. All have a big effect on the motor. The first job is to act like an electronic version of an accelerator pump. The PCM sees how fast your TPS changes, and how far it changes, and injects extra fuel in to compensate for quick throttle position changes. Basically an accelerator pump, but much more accurate.
The 2nd job is to determine the engine modes mentioned above. If you go from a part throttle position to idle (cruising and letting off the gas), the PCM knows you are decelerating, and can enter DFCO mode (deceleration fuel cut off). That's where, after a delay of approximately 7 seconds, the computer shuts off the injectors entirely to save fuel during coastdown. It turns the injectors on again at roughly 1200 rpm to prevent stalling.
Also, the PCM usually has different timing and fuel strategies for idle, so the PCM knowing when you're at idle is important. And then there's WOT. The computer needs to know when you're roughly 2/3 throttle and above, so it can start enriching the fuel mixture from stoich to about 15% - 20% richer than stoich.
The Ford IAC is a PWM (pulse width modulated) signal. The PCM throws voltage at a certain duty cycle to keep the valve open. Once that voltage is no longer sent, the IAC fully closes. This is why if you unplug the IAC, it closes. FYI, GM and Dodge normally use a stepper motor, and unplugging them will not cause the idle to drop. You would have to get them to electronically close before unplugging them, using a scan tool or tuning software.
The Ford IACs are very reliable, in my opinion. Normally, all they need is to be pulled off once in a blue moon and cleaned with carb cleaner and a brush, using care to not let the carb cleaner drain into the electronic half of the device.
Vehicles that have aftermarket cams in them that are lumpy often require more airflow at idle, to compensate for the reduced torque at idle that the new cam has. The tuner can add this extra airflow in the tune, via the IAC. If the IAC doesn't have enough extra room to still raise the idle up high when the engine is really cold and the AC is on, to bring the engine up to say 1800 RPM, then maybe it's time to add extra airflow at the throttle body stop screw (minimum airflow screw). But that might require TPS modification if you turn that screw out too much. Generally, this doesn't need to ever happen. But I do like the idea of setting the minimum airflow screw to where the engine just barely stalls. That ensures you're IAC will be in range, and makes for less work for the tuner in the idle airflow tables.