How can you
not interpret the number of cubits figuratively?
Honestly, you have
nooooo idea what a research project you could give yourself. Any time the Bible starts mentioning numbers, you can pretty well bet that something symbolic is going on. This is considered true in both the Jewish and Christian traditions of interpreting scripture. (I don’t know much about it myself, but I know there’s tons of it.)
Now, how does the general figurative interpretation work? Well, imagine you had a dream that you were watching someone building a house. You wake up with a clear memory of everything you’ve seen, and that you were told to tell somebody about it. So you tell your shrink or your significant other – and they probably see what you can’t. You’re dreaming of a garden that’s exactly the same layout as the cemetery where your mom is buried. You’re dreaming of a living room that’s just like your boss’ office. Stuff like that tells people what the dream is about.
Likewise, the Temple in the vision and its architectural details refers to lots of other things, which scripture scholars are reminded of. A lot of it reminds them of Solomon’s Temple, of course. But a lot of it turns out to be a preparation for God announcing that He’s coming back to dwell among us.
We as Christians know that Jesus is the Son of David (like Solomon) who is Wisdom (like Solomon) – but Jesus is also God come to dwell among us. If you believe in the Real Presence, you know that Jesus does dwell in tabernacles in temples, as well.
So there’s foreshadowing of Jesus and foreshadowing of His Church and even individual Christians (each could be a more perfect Temple than Solomon’s). You can add in a lot more (like the gate only God goes through being a foreshadowing of Mary and Jesus’ virgin birth from her), but that should give you a start.