Hi, Keith. In the past month I'm sure you've figured this one out, but your question got me thinking so I did a little work on it. I put it into a CAD program and here's what I came up with. (I'm unable to put a PDF file here, so I'll explain.) Using 3/4" material, the width across the 45 is 1.06". So 1" or 1-1/8" for jig setting might be a good place to start. I went down to the workshop, found a scrap 1x6 that had a mitered end, and ripped it in half. Here's the mitered end in the jig.
You can see that a 1" thickness setting puts the hole pretty much in the middle of the miter. 1-1/8" setting would move it towards the thicker end of the miter, which isn't a bad idea.
I also put the bit into the jig with the tip just about through the board, and set the stop collar at that point. Just for reference I laid the bit in the jig and lo and behold, it's at the 3/4" setting.
Then I drilled the pocket hole and ran a 1-1/4" screw into the hole. Even going in at a 30 degree angle, there seems to be enough thread to create a strong joint.
Here's the assembled piece. It worked well on these scrap pieces, so it should work in your application.
Now you're going to run into a couple of problems. First of all, you're using short pieces between the apron boards, and there is no room for the long bit and a drill. You'll have to use a shorter bit with a 1/4" socket and a 1/4" ratchet in order tighten the screws. Not a big deal, but not as easy as running them in with a drill. The other thing is trying to clamp them in place to keep them from moving when tightening the pocket screws. I'd be tempted to use a bit of glue and a couple of staples. When the glue dries, run the screws in.
Keith, you've likely read some of the comments from people on these forums who say that pocket hole joinery is just one weapon in the woodworker's arsenal, and it's not always the best one in a given situation. I've rebuilt an old table like the one you're making, and I found that I could drill a couple of holes in each leg of the corner brace, about 3/4" back from the edge, and run a couple of screws through the brace into each apron. Just as strong as pocket screws, and easier to maintain position while driving the screws. Yes, the heads will be exposed, but it's all concealed under the table. The other things you could use are leg braces like these from Lee Valley. http://www.leevalley.com/en/hardware/page.aspx?p=41853&cat=3,43.... These braces, combined with pocket screws from the aprons into the legs will form a very strong joint. Hope this helps.