The specific conditions found with the spark plugs (those which were fouled) are useful in these diagnostics. Were they burned up, gas fouled, or oil fouled, or …? With all those plugs being fouled it’s hard to understand how this engine could actually start or run at all.
Ask your husband to check to see that you’re getting spark at the cylinders. If he finds a no spark condition, he might suspect an issue with the ignition control module, or a bad plug wire, or bad distributor cap, etc.
If all cylinders are getting spark, may want to look at a possible failure with ignition coils for each cylinder. It’s also possible that the ignition timing is the culprit.
Note that the wiring, connectors and actual connections for these parts can be the cause of a failure, too, due to corrosion, wear and/or physical damage, etc.. Also, the same would apply to the sensors he’s already replaced.
Can’t offer more specific information unless you provide the specific on your vehicle, but maybe this might at least aide in pointing you in a helpful direction.
@Samantha Roach Gas fouled plugs tell you that for some reason that cylinder is not firing/igniting the mixture. That means you're running on fewer cylinders and thereby making less power. It also means that fuel is being spent without benefiting the engine, it’s power, your mileage or your pocketbook. Further, this raw fuel then must be dealt with in the exhaust system and probably saturating things in the catalytic converter.
A improper spark plug gap may prevent the spark from arcing, not enough air intake can compromise the fuel mixture so that it doesn't ignite, and an issue with an ignition coil might prevent it from sending the spark at all, or the timing being off might have the spark occurring at the wrong time. In that there’s so many cylinders failing all at once, it seems that generation or distribution of spark, or the timing being off, is more plausible (look for and follow the spark).
The Throttle Position Sensor signals the computer to adjust the fuel settings at the injectors, to maintain the proper fuel/air mixture throughout acceleration and deceleration. It’s actually monitoring how much air is being demanded based on the position of the throttle, which tells the computer how to adjust the fuel portion. A clogged or restricted or obstructed air intake might not be allowing as much air in as the throttle position is calling for, but the computer wouldn’t know that, and increasing the fuel portion would then make the mixture too rich to ignite. This could occur as result of something as simple as a clogged up air induction filter that needs replacing.
When replacing the TPS, know that it’s position is a factor. Use a multi-meter to find the point where the highest resistance/lowest voltage (= to ~0.5 DC volts) is displayed, and secure the TPS in that position. Since this was already replaced, ask your husband if this was taken into account. If not, he may need to reset the TPS’s position.
Also, be aware that the throttle body itself could be contributing to the problem simply due to needing cleaning.
Hope something in this might help. Please keep us posted.