You're so wide open with your (lack of) requirements that it's hard to make a suggestion. I don't quite know what you mean when you say your organize with Calibre — does that mean you organize your books in Calibre and just move them over, one by one, to your Sony as needed — or does it mean you more closely integrate Calibre and your eReader?
If you organize in Calibre and just move books to your eReader as single books, not collections (and don't mind a used eReader) I would look into the Tolino Shine 2 HD (300dpi) eReader I've suggested elsewhere. $30 and $7.50 shipping (you could probably make an offer of $25). These are fairly sparse in features but it's a nice quality eReader.
https://www.ebay.com/itm/Tolino-Shin...ox!83646!US!-1
I use one and like it a lot (but I like Tolino readers in general).
There's also the option of repairing or having your PRS-T3 repaired. There are several sellers (both on eBay and Amazon) who sell replacement T3 screens. The cheapest I've seen on eBay is $22 (without the tool "kit") and upwards to $36 with it. The cheapest on Amazon appears to be $40 with the little screwdrivers, etc., you'll need. There are also YouTube videos that show you how to do this. Lots of little screws but, with patience, it looks like it could be done relatively easy.
Also, since you buy your books from Amazon, the newest Kindle Basic (with front-light now) will probably be on sale for around $65 for Black Friday. It uses a 167dpi screen.
There's also the Kobo Aura Edition 2 at Walmart that sells for $70 (it has has gone on sale for $50 in the past). This one uses a 212dpi screen.
There's lots of choices. Since your required features are so wide open I've just suggested some of the cheaper options.
Good luck.