Songs: https://www.hooktheory.com/theorytab

Music Theory site:    https://www.musictheory.net/lessons

Free notation software:   https://musescore.org/

Free Recording and editing software:  http://www.audacityteam.org/

Some free and easy guitar lessons. Good to use as a reference if you need to play some scales or if you need an easy song:  https://www.justinguitar.com/

                Scales: https://www.justinguitar.com/en/SC-200-TheMajorScaleIndex.php

Chords: https://www.justinguitar.com/en/CH-000-Chords.php

Recommended books:

Sight-Read Any Rhythm Instantly
by Mark Phillips
Link: http://a.co/gmKgKhX

For Rhythm practice:

Progressive Steps to Syncopation for the Modern Drummer (Ted Reed Publications)
by Ted Reed
Link: http://a.co/6a3U1ep

Improvisation:

Developing musicianship through improvisation by Chris Azzara

excerpt here

http://www.giamusic.com/products/dmti_books.cfm