Wow - you remember my 10k. Yes, that was the one race that indicated 2.45 was maybe possible. My half time from January indicated something a bit slower. Come race day I wore a pace band with mile splits and used my garmin to check pace for each mile. Meant really focusing especially when I got tired.
No, I mean I was about same level as you are now when I was training for London. Also all of my training and most of my races indicated about 2.48 at best, but on the day i just went for it. As long as you keep training smart you should do the same. May as well just go for it.
Yeah, it's a real big jump. I think need to progress to it. When I went sub 3 I think took another 2 (or 3?) marathons before just managing to squeak under 2.45. Running 6.17min/mi feels a lot faster than running 6.50min/mi.