Any question answered...

Re: Riding without headset spacer

If the threaded top race is tight enough it will be fine to get me home right?

Too late have to leave it :(
From your description, it sounds like you have a threaded steerer, but no way of tightening up the upper cone/race against a locknut. This means that should you ride the bike, the top race will almost certainly become loose.
Depending on your personal preferences, you may ride the bike and hand-tighten the headset as you go. The looser it gets, and the longer you leave it loose, the higher the probability that you will damage the headset bearings/races.
If it's a beater with a shitty headset that one would replace anyway, I'd go for it.
If it's a pristine vintage Campag one, then I'd think twice.
YMMV.