Kindle Unlimited or not?

NOT how it's getting printed!!
I need your help and advice, guys. At the moment, Lies That Poison is only available via Amazon. Technically it can be ordered in any bookshop, but practically, I know this is unlikely to happen. One of the reasons for the Amazon exclusivity is because I'm on a vertical learning curve and I only wanted to sort out one format (Kindle) rather than other formats as well. Likewise, the 'getting it printed by IngramSpark' aspect seemed as if it would not be a good cost/benefit ratio - both in terms of how much time it would take me to get it ready, and the cost to get physical copies to me/stores in comparison with the amount of sales I would make. I believe that the number of physical copies sold anywhere other than Amazon (whether that was a bricks and mortar store or me taking books to a book festival or whatever) would be small.

Of course, that does mean that I am feeding the behemoth that is Amazon and not supporting local physical bookstores. (Mind you, my local independent bookstore was so vile to me when I asked them if they would stock my books, that I don't actually mind that so much!) My local Waterstones have been helpful - both in helping with launches and with stocking physical copies of my books in the past. They may be less so when the Amazon-printed books say that they're printed by Amazon on the back page. I'll need to see. But again, the level of sales via them will be small and the cost of getting them printed and shipped via IngramSpark may not be worth it.

So, at the moment, Lies That Poison is only available from Amazon, which brings me to another quandary... Kindle Unlimited or not?

It is on Kindle Unlimited (KU) at the moment, so I get paid for the number of pages read when people borrow it. I went for that, because my royalties statements from Joffe Books always indicated that I made more money via KU than sales of physical copies (even in those halcyon 6 months when I actually got decent royalties). But what I need help with is some market research. For those of you with Kindle Unlimited, do you tend to still buy books, or just use the KU feature? If a book wasn't part of KU, would you buy it or would you skip it? (I'm talking about books by authors like me... obviously people may buy books by famous authors if they're not on KU, but that's different, I think).

I'm trying to work out whether to keep the book in KU after its 90 days or not. At the moment, sales and income from KU are similar, with maybe KU having a slight edge. My fear is that if I pulled it from KU, I would miss out, because people would tend to just find another 'free' book instead, rather than buying it. But, I'm a scientist, so I'd quite like to make a decision based on data, not just supposition.

So, my question to you all is: if you see a book (by an unknown author) is not available on KU, and the blurb interested you, would you buy it anyway? Or would you think that there are a gazillion books available via KU and find one of them instead (I do see that there is a filter button on Amazon  to limit searches to include only KU books)?

Thank you in advance! If you could let me know in the comments, that would be brilliant.