Power steering keeps going stiff all the time

What year is this Focus? First you need to work out what the "Clonk" is. Is this clonk only as you turn or does happen when you hit pot holes? The most common reason for a steering/suspension noise is one of the joints on the system. Get the bottom ball joint, the track rod ends and the drop links looked at.
If your car is before 2011 check the fluid level in the power steering. After 2011 they changed to electric power steering. Sometime the stiffness is that easy to fix. If you need to top it up only fill to the MAX line. After topping it up, With the engine running, turn the steering all the way to the left then all the way to the right and repeat it 3 or 4 times. This bleeds the system.
If the joints are all OK you need to look at the actual steering rack.

thee is a correct method to fitting power steering hoses to prevent this It is just not a matter of putting it in and tightening it up
Take it to a steering specialist shop to ensure that the fitting is correct and have it done,

I don't know what a "early" sound is, but there are several problems that can cause a screech: the commonest is a slipping power-steering belt combined with a stiffness in the steering rack. The cheapest is probably a stone caught between the brake pads and disc. So first check your tyre pressures, then check your brakes finally, take it to a garage to have the power-steering looked at.

Make sure that the power assist oil level is at correct level.

Answered

Check the power steering fluid, also check to see if your belts are in tack and powering the motors.

Heavy as in ,stiff steering?
Not usually the pump. It's only money.
Lets go with a worn steering rack,after you check out the strut bearings,being worn/stiff etc.

have you checked the power steering fluid maybe the pump too

its apossibility that when you got new top strut mountings fitted it might be fact that it will be like new & you are not used to it also not having power steering you might be feeling the effects what i would suggest you do is continue to drive itnormal & see if it eases of if this doesn't sound like problem & stiff through column or steering rack let me know because not been able to feel it its hard to tell thank you.

Most cars Speedometer cable connect to one of the front wheels, but you said your speedometer sometimes stop then your steering wheel will go stiff, I think you should fix or change your speedometer cable, maybe the cable broken inside. Fix it as soon as possible for your safety.

Speedometer cable has two parts, one is outside cable, mounted and connect to both speedometer and wheel.

The other one is an inside steel cable, outside cable protects the inside cable, because the inside cable turns as soon as you move the car. It is directly connect to the wheel gears and the speedometer inside.

If your car has speedometer cable, I think you need check it right away.

Your steering wheel sometimes stiff, you also need to check your power steering fluid level, sometimes cause this kind problem.

Hope this can help you and if you have more questions, please use whatever the Fixya allowed, contact me to discuss this matter and others. Thank you.