To answer your questions based my local experience.
Are secondary school counselor jobs secure in the economy? No, every district in NY State is currently laying off, including counselors. There are many reasons, but a big one is that the state has significanly reduced state funding to local districts. It is my impression the the state is trying to force mergers, consolidation and large regional/county schools similar to what you see in Florida. The point is that funding is going to stay low, budgets will continue to be tight and there will be more mergers, layoffs etc.
Are there good prospects? It depends on what you consider good. Compared to the prospects for VCR repairmen, I guess it would be good, but compared to jobs in the healthcare field I would say no.
How competitive are the school counseling grad programs? Are they tough to get into? No, if you're willing to pay the tuition, you're going to get in. As someone who works in higher ed, I can tell you that schools will take just about anyone willing to pay grad school tuition. The only grad programs that are going to be difficult to get into are medical/dental, law at the top schools, business at top schools, etc. Beyond that, it's pay to play.
I'm not saying that you definitely shouldn't pursue school counseling, because that is a personal decision based on a lot of factors. However, I am advising that you should be aware of the cost vs. potential. If you read these message boards, you will see hundreds of stories of people who thought that they would beat the odds and a get a job, and some do. But many more will accrue thousands of dollars in students loans and years of energy studying, for a degree that they will never use. Most of them are probably smart, hard-working people who would be great counselors the problem is that we have too many people and not enough jobs. Good luck with whatever you decide.