James some resources for you.

The time signature may be how some of the things translated from program to program and how it interpreted things

So it goes as follows -

1 Mp3 extracted from Youtube
2 Mp3 into Reaper and Melodyne added as an FX on the channel
3 It has a polyphonic setting and just reads the file in and will import pretty much anything and return you the notes so you can fix/change manipulate/do what you want. It's probably the most astonishing piece of software I have ever come across. Mostly used for tuning vocals etc in mixing but you can pick out and change guitar note pitches in a tune with multiple parts. Just astonishing! There are some odd notes that could be tidied up but I don't think it's needed.
4 Exported the file to midi and imported it into Musescore

Things for you that may help or not. The video is what Melodyne worked out and then me just playing the file in real time and making a little screen grab/video
MELODYNE OUTPUT
MUSESCORE FILE
MUSESCORE PDF

IMHO - I reckon it's a bit like playing Stairway to Heaven - ie no capo Am shape at the fifth. Then a lot of the things just seem to walk down the guitar. It isn't a "using the bass notes" sort of tune. I like the bits where it flips between B and Bb and the odd bits where it throws in an E major if I remember. Perhaps Jimmy Page got it from here rather than Spirit - he was partial to a the odd bit of folk I believe

All good fun

You'll be telling me that Blackwaterside is in DADGAD next