1. I'm not getting this on my end, except for "smart" auto-completion mode, which shows ef_ellipse and a few other options (as keywords are not currently among the auto-completion suggestions). Was this on the current beta? (which I have now also pushed onto stable channel)
2. If you mean Ctrl(Cmd?)+Shift+F, I'm not seeing that on my end, so please elaborate.
3. See if that works in regular Ace.
4. I intend to implement this, but some additional checks are required, as I do not want a side effect similar to what is seen in Inkscape and some other software (where, if you change a monitor configuration, a window may open completely off-screen)
5. This is by design - pretty much everything in GMEdit happens at the exact moment of saving, be it indexing, syntax checks, or syntax extension hooks. Rewriting this to speculatively evaluate changes in real-time is possible, but expensive.