We get a ton of convos each day, and I have taken to simplifying convo-answering as much as possible. Here are some things that might help:
1. I have an FAQ in the policies. Because the policies are a tab on every listing, I think some people do read them; if I'm in a hurry and a convo is asking things that are answered in the FAQ, I just say "you can find that info in the FAQ, here: [link to policies]" If they ask something that's answered in the listing, I say "you can find that info in the listing description, here: [link to listing]"
Do you use saved snippets at all? It might still be a prototype - if it is, join! If not, use them! Either way, they are a huge help.
Also, develop a process or even a listing that guides people through some of the common custom changes you make. I see that a lot of your shop (like ours) is already custom; I looked at a couple of your sold items that were created as custom orders and since I don't know your business I'm not sure how you can simplify it - if you want to convo me, I'll tell you how we do it and maybe you can analogize?
Maybe part of it is that we only answer convos once or twice a day - I could not, ever, answer a convo within half an hour (unless it is during the convo-answering window).