Not sure what you've been smoking. The lad's comfortably onside - by a couple of yards. Williams playing him on.
No it's not that clear. It's difficult to assume a line with that angle. If the lino is in line with the last man (which he should be) then it is a very close call.
I might be barking up the completely wrong tree here but the columns of seats in the east stand are perpendicular to the pitch right? As in A10, B10, C10 etc line up with each other at right angles to the pitch. If we accept that then this crudely drawn line gives a rough indication of what the line across the pitch is I think?
You're not allowing for the pitch of the seats. Your line would be right if the whole stand was at ground level.
They are perpendicular to the pitch but they're not flat, so you can't use them like that. The easiest way to do it is to draw a line between the defenders' feet. There's no way a player behind that line can be offside.