1. Yes. But you could end up making all your SS taxable based on how much your total income is.
2. Many companies are doing this. Moving elsewhere as someone suggests is hard because very few companies even offer pensions anymore. The biggest benefit to companies abandoning pensions is that most pensions also help pay for medical, while contributions to a 401K are just that, cash contributions only. No other obligation. (I would also seriously consider taking the pension in a lump sum payment when you leave.)
3. One thing to be careful of -- if you max out early and stop your contributions, so will the company's matching contributions. They match based on each specific paycheck. So, if you are not contributing for a paycheck, they don't match. For instance, my company matched the first 6% I put in (and 50% of that) per paycheck. If I put 5% in for a paycheck, they match half of that 5%. If I put 7% in for a paycheck, they match half of 6%. If I put nothing in that paycheck, I get nothing from the company.
My company had separate items on the contribution form I had to fill out -- pre tax contribution and post tax contribution. I set the post tax contribution at 6% and left it for the entire year (so, I wouldn't forget to change it when the pre tax money capped out and thus wouldn't miss a company contribution). Then, I set the pre tax contribution including catch up as high as I could afford to max it out as quickly as possible (after all, you want the money in your investments doing their thing as soon as possible). Then, when the pre tax maxed out, I still had the minimum contribution for the company match in the post tax.
See if your company has separate items in your form like this. This would alleviate the situation you got into.
Oh, as to your general question, put in as much as you can afford, pre or post. You'll thank yourself when you turn 80, 85, 90...