good news it's all running nice again.
did you notice anything (dirt etc) come out of the carby when you sprayed that Pilot Jet port ?
with the exhaust,
if you lock some decent vise grips onto the stud, you should be able to undo it and take it out the head
then you can either replace it with another stud (high tensile M6 x1mm pitch),
or use a M6 x1mm pitch bolt, it will need to be a bit shorter than the stud that you have taken out, maybe use some spring washers to space it if you need to?
in your pics of the oil leak,
i can see it looks to be coming from the camshaft cover on the l/h side of the engine ?
it might need a new gasket there ?
or it might just need the centre bolt to be tightened up a little, don't strip it by doing it up too tight!
the bolt is on the r/h side of the head in the centre of this cover
possibly the rocker cover at the front of the head is leaking? 4 x 10mm headed bolts
or maybe the round rocker cover on the bottom of the head is too?
they use an o'ring to seal against the head, auto parts shops sell new ones, or a industrial bearing shop.
if you degrease the front and underside of your engine and wipe it clean, then just keep an eye on it regularly to see where it is leaking from.
also check if the Oil drain plug, or the Timing chain tensioner bolt needs nipping up a touch.
if you were to take it out, there should be a thick copper washer between the bolt head and the engine case.
you should be able to pick a couple of new ones up from any auto parts place for under $1
or the other way would be to use some thread tape, but it shouldn't really need it.
and when you add pictures from Photobucket etc,
you don't need to click on the add pictures box, above the text box too.
see your second lot of pics have