1. Most never ask ourselves if and how television might hurting us.

Question

(Do we have to use 'ourselves'? How about 'themselves' in place of 'ourselves'?)

2. Below you will find the costs and benefits of watching television.
(Does 'costs' mean
'disadvantages' here?)

3. Some blame "the" television for society's violence, consumerism, and misinformation.
(Do we have to put 'the'
before 'television'? What about deleting 'the'?)

Answer 1

1. You would use "ourselves" only if the subject were "We" but since the subject here is "Most" then "themselves" is correct.

2. Yes, costs are what we PAY and benefits are the good things we RECEIVE from whatever the sentence is about. So, yes, costs could mean disadvantages in this context.

3. You can either keep or omit "the" before "television" in this sentence. Either way works fine.