I'd recommend Mark Todd Auckland breeches with long boots - had mine for ages, worn them in all weathers...comfy and durable (albeit a bit faded now!).
Sounds like you have a sweet horse who has just had a bit of a fright. Whilst a new lorry may not seem like a big deal to us, it's full of unusual smells and unfamiliar fixtures and an unfamiliar confined space which eliminates his 'flight' option once he's in.
I would go back to basics - baby...
I've found that the terrain rather than the distance makes more of a difference at this level. So, a 32KM ride across the fells in Cumbria for example is likely to be more challenging than a 40KM ride across gently undulating terrain with decent footing.
If your horse is fit (and it does sound...
Suggest you ask your vet to take skin scrapings to rule out any parasitic causes. Also look up Follicular Dysplasia - a genetic condition which causes alopecia. Dogs with this condition don't show any significant signs of itchiness or discomfort, but it is often progressive and permanent. Hope...
I really like Buck Brannaman, and use his approach when I can. It has really helped with bringing on a couple of youngsters, and helped me developed a great partnership with the mare I ride.
I watched all 3 days of his clinic at Aintree last year, and really enjoyed observing his common sense...