how much shorter will a 0.5 deg headset actually make your reach?
Remember that when you slacken the forks the front end will drop which makes the reach longer. That is assuming you can remove enough spacers to make up for the external top cup if you didn’t have one before.
I am not sure I would bother with 0.5 deg. Go the full 2 deg or go home 😉
2 deg will actually be about 1.5 deg and IIRC about 5-8mm lower BB and a slightly steeper seat tube.
If you have the space on your saddle rails then whack it back a bit to get more length, you wont get the benefit of a steeper head tube but will get more reach. Other little things like slightly adjust your bar rotation to take out some back sweep, longer stem etc can be used. Although when I added a 2 deg angleset I went even shorter to get the steering response back up. Running longer than 50mm feels odd to me now!