It would be better to say 'Have you ever wanted someone to correct your writing?' As the context of the sentence is probably not isolated in specific past time but means at any time in your life up until now. When we ask this kind of question using 'ever' the verb tense is usually present perfect. 'Have you ever been to New York'. 'Have you ever stayed awake all night?'

It should be 'Did you ever want someone to help correct your writing?'

Take out the first "to" and it's correct; it's not needed.

Want somebody to do something. Reply the letter and tell Italki they should learn some basic English.