Yes spring is a bit manic with everything happening at once! Good luck with the fruit trees - what pears did you get? I haven't got any pear cultivars yet, but I planted some wild pear to hopefully graft onto.
The smaller the greenhouse the bigger the swings in temperature. It is difficult to manage - increasing ventilation as early in the morning as you can on sunny days, would be my first advice.
I found blueberries need fairly aerated soil and sunshine. My first bushes just faded away but once I planted them on minihugels they've been good. I have high hopes of a reasonable crop this year. Well it looks like plenty of flowers anyhow - we'll see if the birds and the mice leave me any fruit! Raspberries are usually pretty easy in Scotland too - just let them find their happy place and don't let nettles form the ground layer!
As regards windbreak trees, my first advice would be to get as local tree stock as possible. Commercially available trees are either unspecified, or grown for forestry projects, so will not necessarily grow as well in your location as a locally adapted tree. I have found alder and hawthorne relatively quick and rewarding. Elder has been slower to establish, but is very tough when it gets a bit bigger and is also useful for flowers and fruit. The chestnuts I got didn't like Skye at all, but I have strong salt laden winds off the sea, so many of my trees suffered from dieback until there was more shelter- even tougher shrubs like Hazel (which would be a better bet if you want nuts I suspect). Saying that, several of my chestnuts are still alive - although at a maximum of 12 feet or so after 15 years - I'm not expecting good harvests! I also quite value my spruce and pine for the shelter they provide. If you have the space they can be very effective at giving shelter, often seedlings are easy to harvest from plantations as they seed into the paths where they will be mown down as weeds.
Landrace gardening I feel rather evangelical about, although it is early days for me. I'll point you at a couple of threads to read and you'll get lots of answers there. The basic idea is that open pollinated heirloom plants are better than F1 hybrids, since you can save true to type seeds from them, landrace seeds are better than open pollinated heirlooms as you don't have to worry so much about cross pollinating (in fact it is actively encouraged!) and you will get a diverse mix of plants that adapt to your own growing style and location. If one seed does poorly one year then another seed will do better to make up.
https://permies.com/t/31939/Landrace-Gardening
https://permies.com/t/54028/purity-seed-realized-Seedy-Saturday
and free seeds for starting your own land races:
https://permies.com/t/240023/catch-free-seeds There is a UK arm to the 'going to seed' organisation and you may be close enough to the far North seed savers to take part in their swaps too.