Hey Haewon!

For your first question, it is NOT correct to say "he is taller than me." You must have a subject-case pronoun when making comparisons. The reason for that is if you flipped the comparison around, you cannot say, "me is taller than Jack." You must say, "I am taller than Jack." 

Note: when using "like" as a comparison phrase, you use object-case pronouns.

ex. Like me, Jack is kind. (correct)  Like I, Jack is nice. (wrong)

When using all other comparison phrases (smarter than, as smart as), use the subject-case pronoun.

Jack is as smart as I am/she is/they are.

For your second question, it isn't wrong to repeat the "had" in the second example. Sometimes, you will see writers do this.

ex. I like to run and to swim.  

However, if it doesn't appear in the second example, the word "had" (or whatever other word in the first example) carries over to the other examples in the list.

ex. I would play basketball and study math on the weekend. --> I would play basketball and (would) study math.

Hope this helps!

Keep moving forward!

You got this!