"Are there any pictures of these “spiders”
Yes. People have posted some online. Calling them spiders doesn't seem very accurate. They appear more as a cross between a locust without an abdomen, a spider, a bit of upper end of a praying mantis. They seem about the size of a quarter.
"...do they match any description of a creature in the book of knives?"
No specifically but there is just barely enough info, combined with things you know, that you could deduce they are associated with Kormaca, and apparently grow into one of several different things. ...think it's the last two on the daggers pages, and another one. ----I'll try to finally get around to that all a bit more.---
"How does the alignment of the LA gate match with the wildfires or area water tables?"
The fires in the mountain area would seem a bit off, but if you give Andre a wide enough margin of error, it's roughly there. Or maybe possible the forest mountain area just ignited sooner.
"What do we do about the rain?" ...an umbrella?
"How can we pinpoint where the gate was opened originally." There would not seem to be a way to.