1. I think you are underestimating the number of people who would jump at the chance to hurt Superman. The big shots you mentioned may be uninterested in striking at him through his family, either because they are too honorable or simply because they see Superman's parents as unimportant bugs, but there are countless small fries who would love to get back at Supes for thwarting them, or simply because supes makes such a great taget.
Darkseid may leave the Kents alone to focus on their son, but Random Thug #2765725431, or Random Drug Lord #3764732, or any Random Criminal in general, may easily decide not to.
2. Fair point. But even so, a secret identity offers a lot more freedom: you can just be carefree instead of having to disguise yourself and act inconspicuous.
3. As far as I know, he doesn't want to be a blogger; he loves writing for a newspaper, and so does Lois. Also, I think he wants his work to be appreciated for what it is, rather than for who he is (that is to say, Clark Kent has to write genuinely good articles to get them published and awarded, whereas anything signed by Superman would instantly be a best seller regardless of its actual quality).