Hello Marcus,
I don't think that midi knows about a partial bar, and you may need to use a full bar and start with a rest of appropriate length. That is, in effect, what the music is doing anyway. Otherwise you'd need to use a different time sig for the first bar, then set 2/4 at the start of the next bar, and see what that does. But, why didn't the composer do that? Is there a difference?
As for the grace notes, there may be a complication if there is a difference between what Anvil will allow you to enter, and what midi will accept. Certainly midi can accept grace notes, although they may need to be 'tweaked' into the data after other things are done, and certainly after any Quantize has been done. You might need to adjust the midi note resolution if it will not initially accept the notes (will they end up as 16th, or 32nd, or less ?). When I've tried to play something into midi to record, I end up with a mass of such notes. I've looked at some of the pieces in the 'Classics in Sequence' book I mentioned before, and there are grace notes there, although not quite as small as you've got here, but the only comment in the notes is that they need to be added afterwards, esp after Quantize is done, so any problem is just the problem of getting them in.
Do remember. Composers certainly take liberties with the score, and performers will do likewise for 'artistic' purposes. Why should you be different?
Geoff