The latter of the two is better as you say. Regular smaller chunks rather than 10 hours over a weekend... you'll only hurt yourself. Having a regular routine is good, then move on as you master bits.
11th and 13th chords - anything from a 9th onwards is in the 2nd octave (play a 2 octave major scale to help this along), so a 9th is the same as a 2nd, 11th the same as a 4th, 13th the same as a 6th - just played in the second octave...
All built with triads - a full major 13th chord for instance would have the root, third, fifth, seventh, ninth, eleventh and thirteenth scale degrees, although obviously that's more notes than you have fingers, so some are dropped...
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