• 12.009 and find this beastly tunnel was my own front-hall at home!’

This is a JRRT original.

• 07.133 early on the fourth-day,

Just so.  A compound word, not a counting word followed by the name of the thing being counted.  Hmmm.

It is an attested compound word, specifically coined by the Society of Friends to mean “Wednesday”.  Beorn did not mean “on a particular day of the week”, but “the fourth day of your travels from here.”  I’m calling a JRRT-original use.

“four, adj. and n.” OED Online, Oxford University Press, June 2017, http://www.oed.com/view/Entry/73969. Accessed 13 September 2017.

• 05.053 four-legs got some.

This hint at “cat” is not attested in OED, although my mother-in-law often calls the four-legged members of the family this.  “Four-legged”, by the way, is in the dictionary.

“four, adj. and n.” OED Online, Oxford University Press, June 2017, http://www.oed.com/view/Entry/73969. Accessed 13 September 2017.

• 07.151 Stick to the forest-track,

Unattested in OED.

• 06.045 and the forest-silence deeper.

It’s a very particular kind of silence, not attested in OED.

• 08.004 There was no movement of air down under the forest-roof,

A word not attested in OED.

• 10.006 the forest-river rushed into the Long Lake.

A word not attested in OED.

• 06.045 and all the while the forest-gloom got heavier

A word not attested in OED.

• 07.133 that they should reach the forest-gate
• 07.143 they found close to the forest-gate,

A word not attested in OED.

• 08.076 of the forest-day about him when he came to his senses.

A word not attested in OED.