Welcome to the site, it's a cracking car, and once sorted, and remapped it's a peach. I'm by no means the font of all knowledge on these, but having the same car and engine, I'll give you the benefit of my experience.
1st and 2nd are a bit sluggish -3rd and 4th are the sweet spot I find, but it should pick up from about 1400rpm in most gears - just try and keep the turbo on boost if you can.
Not entirely sure which bit oil is leaking from, mine mists from the bottom of the oil filler neck - but the vacuum pump sits directly in front of this, and has also been known to bypass a bit of oil.
Smoke and vapours could be a DPF fault - make sure it's up to temperature and that any vapour goes away - a bit of white smoke on start is normal though.
Rough idle could be a multitude of things, bad, dirty injectors, clogged intake, list is endless, then again, it's not a smooth idler compared to most diesels, and a bit of clatter is normal with these, servicing with good oil and maybe a couple of tanks of premium fuel, or a dedicated injector cleaner might even this out.
Dual Mass Flywheel (DMF) can cause a rattle, which means it's on its way out - but it sounds particularly loud from passengers wheelarch side - it's a bit bill if it's gone, as means new clutch and release bearing also - plenty of threads on here about it, including a couple of vids - alternatively, it could be the crank pulley/vibration damper which tears over the years.
That aside, does if have much service history - were the cambelt and water pump replaced in the last 40k miles or so, any evidence of clutch/flywheel work? - and lastly, if you can have a look at the subframe, or whatever is exposed - they're known to rust and again is a big bill.
Posting from my phone - excuse spelling mistakes
Last edited by amfalconer; 02-04-19 at 14:02.