I don't have a book or blog to recommend but I can tell you what I've learned from my experience.
By way of introduction: I have two hoophouses. One is 32x12 and the other 28x12. I live in Zone 5b, up in the mountains of Northern New Mexico. I think you are in Zone 5b as well.
Hoophouses, greenhouses and tunnels (low and high) give the most value at the margins of the year. That is, they help you get started earlier and let you keep growing later. In many climates they don't offer as much value during the high summer months. In some warmer climates they can become unusable due to excess heat. But, during high summer they do provide value in cooler climates. They keep your plants warmer at night which leads to increased growth. They also heat up faster in the morning.
I have the same experience with tomatoes as you. Outside, they putter along all summer and when they finally start to bear fruit, here comes the frost. But in the hoophouse I can get a couple of months of nice, tasty tomatoes. They don't come as early as they do in some places, but it's still much better than I would get growing outdoors.
One of the keys to success with a cool weather hoophouse/unheated greenhouse/tunnel is to get your plants started early indoors. I start my plants under lights in March/April. Things start to warm up in May and I move them into the hoophouse during the day. Eventually I can leave them out there overnight.
One of the great uses of a hoophouse/greenhouse/tunnel is to get your outdoor plants a headstart. I can't plant outside until early June but I can get them going much earlier by using the hoophouse as an intermediate stage between my seedling rack and the garden.
To answer your specific questions:
Your tunnel becomes too hot when your plants start to droop and their growth slows down. I like to keep my hoophouses below 100° but that isn't always possible. Things seem to be OK even with a few periods of >100°. But I don't like them to get above 110°. But that hasn't happened since I got my fans and shade cloth dialed in.
Leave the hoops on at night if your night gets cool, like <70°. You plants will set more fruit and grow faster.
Watering is the same as always except it will be less frequent due to decreased evaporation. Your sensor should help with this. The general advice is to water when the top 1" of soil is dry. But you can vary this according to climate and crop. Experiment, but remember you can easily overwater in a tunnel/hoophouse.
And they are ideal environments for fungal growth. So, watch your water, don't over do it. Make sure you have a lot of air circulation (I use solar powered fans and solar panels). And don't crowd you plants. Plus practice good garden hygiene. They are also great environments for many bugs, so inspect your plants regularly and take action immediately if you find a destructive pest.
Extra advice at no extra charge: I don't know how high your tunnels are, but if you're growing tomatoes they might not be high enough. You should know that you can put supports (fencing, trellis, wire, etc) in the tunnels and train your tomatoes to grow sideways rather than up. Just to give you an idea to work from, here's how I run tomatoes up my hoophouse walls with wire fencing.
If you don't find a book to your liking come back here when you have more questions. You should come back here anyway. We love to hear garden stories. And we really like pictures!
