Surely you want the spider slightly angled so top E is nearer the neck than bottom E to get a reasonable intonation? Which might mean that the spider is a now a bit too near the neck if the scale length is correct in the middle? And you'd normally need a longer length than the nominal scale length.
For a 642mm scale length, the StewMac calculator gives the nut to saddle distance of
Treble "E" or 1st string: 644.238mm (± 0.5mm)
Bass "E" or 6th string: 647.402mm (± 0.5mm)
...which is approximately a 3mm difference at the two E positions. With heavier strings (which you'll want for slide), then the bridge will need to be back a little bit more.
If you play purely slide, then it won't matter too much as you can compensate for distance and angle (though it makes it harder work). But mix some slide with some fingered notes and you really want the intonation to be as good as possible.
From the photo, it looks like that it's about 5mm too short a distance from the nut to the leading edge at the centre of the spider.
What you don't want to do is glue the neck on now and....