Possibly some air in the fuel filter .... if it has a priming rubber bulb then this should be firm at all times, if it needs pumping up then you have air trapped in there.
First point would be to check all earth points on the underside of the vehicle.....have had issues with Nissan's suffering from broken earth straps from the battery to the chassis and transmission
I wonder if you should take it to another garage - one that specialises in four wheel alignment
The suspension should always first be adjusted from the rear (if there is adjustment possible) otherwise I can't see what the issue is (accident damage aside)
Try this site....should have your car listed
https://www.castrol.com/en_gb/united-kingdom/home/car-engine-oil-and-fluids/motor-oil-and-fluids-finder.html
First thoughts....do you rest your foot on the clutch pedal at all?
If so, then you have worn the release bearing and this is the reason for the sound.
As long as it doesn't get any worse then it should still be good for a while
You can find suppliers on eBay for stainless steel custom exhausts much better than original and not too expensive either
Usually drive there and wait while they build you a system (or part system)
It depends on the age of the vehicle but it should be fine to just fit and then reset the audio system security code if necessary
Disconnect the negative first and reconnect the negative last
Ensure you have the keys to hand then lock the doors and unlock (may take a few presses of the lock button initially)