V50 Strange vibration at certain speeds.
 

Hello.
I have a 2005 Volvo V50 2.4 with a little vibration issue.
My steering wheel starts vibrating at around 120km/h and only vibrates at that speed. I usually drive 110km/h on motorways to avoid this issue and even save some fuel. The vibration is only felt in the steering wheel and I can feel no vibration going through the body of the car whatsoever. It also feels like it's from the left (driver's) side of the car in the front.
The car runs perfectly smooth with no vibration at all at other speeds, for example 80km/h or 150km/h, which makes me believe that it's not the wheels (New wheels and recently balanced).
I have also recently put 30mm lowering springs on the car but it had the same vibration before with factory springs.

What I know:
- My DMF is worn out and clicking a tiny bit on idle and my clutch also needs replacing soon.
- When I try to move the drivers side driveshaft with my hand, I can hear a little tiny clicking noise when trying to push it in or outwards.

Some time ago when I was going over a speed bump at very slow speed (less than 5km/h) I heard a silent bang from the front of the car. (thought it was a rock or something touching the underside of the car). Since the same evening, I have felt that the clutch pedal has a point in the middle of the range where the clutch slips a tiny bit, and then keeps on releasing normally
I had always thought this was a symptom of the clutch being worn out, but now it makes me think that an engine mount could have broken, and that causes the vibration at the certain speed and also the little judder in the clutch when you set off. Could it be an engine mount? If so, how do I inspect the mounts without being able to hold the engine up right now to remove the mounts?

Thanks in advance, Jon