Ou plutôt, il y a plus de livres que les d'heures disponibles.

ou encore "il y a plus de livres que je n'ai d'heures disponibles."

Quand j'étais petit, je lirsais tout le temps.

"je lirai" : future, I will read
"je lirais" : conditionnel, I would read
"je lisais" : imparfait (past tense for continuous or repeated actions), I was used to read

Mais maintenant j’ai beaucoup d’obligatione responsabilités.

Or maybe one of : "contraintes", "engagements"
I think people would understand you, but "obligations" is kind of weird in this context in french. This word is usually used to designate either a certain type of financial product, or a concrete engagement.

Donc, il n’y aje n'ai pas dle temps pour me détendre etn liresant un roman.

ou bien "il ne me reste plus de temps pour"

"détendre et lire" (chill and read ?) is a typical English construction that does not translate well to French :)
In french "et" is really for addition of things, never a logical conjunction.

Dans l’avenie futur, si je peux, je lirai plus fréquemment.

"Dans l'avenir" : can't see a use for this expression, not even for a medium
"À l'avenir" (I guess this is what you meant) the expression exists, but it somehow implies a logical connection : I learned my lessons, but in the future I won't repeat the mistake.

Quand je réfléchis aux années passées, je souhaite que j’aurais lurais avoir plus lu.

Don't ask me, I am not Mr Elephant :)
I can hear the music of the language, I know what is right or wrong, but I have no idea about the rules I follow :)

My guess is that this is a wish... "I wish I had" => conditionnel, and this is a conditional in the past... "souhaiterais avoir lu"... Makes sense...

En tant qu’ado, j'ai gaspillé tellement de temps sur Internet et les réseaux sociaux.

I have the feeling gaspiller is more related to concrete stuff. For time I would use "perdre".

Si j’avais lu plus, peut-être que j’aurais pu apprendre plus.