Pants: Timberlines are pretty hot for sheep opener in the North unless it's real cold. I've got 140+ days in a few pairs of them from 30º to -20º and I think they really do well when it's 5º and colder. I tend to run on the hotter side, but you'll be sweating like a mofo in them if its over 15º out. Lighter pants and merino long underwear go a long way. Kuiu makes some great lightweight merino & synthetic zip off long johns that do not require you to take your pants and boots off - not a game changer but sure is nice.
Sleeping bag: If you don't already have a decent sleeping bag, a single -9 bag will cover most of your backpack hunting needs. Down is superlight and packable, higher warmth to weight ratio, and today's hydrophobic down bags are pretty damn good. Synthetic is far more versatile, and way less expensive, but bulkier and heavier. Your choice on whether you value ultralight or versatility. IMO going full ultralight isn't a smart choice. Durability will always be less, and versatility in shit-show weather isn't great either. I sometimes run a 0º down bag while sheep hunting in august, however, im usually only a days hike from horses and a wall tent with a -18º synthetic bag in it.
Boots: Assuming they fit your feet well and don't give you blisters, the Lowa Tibet will be a better choice for sheep hunting. Far more durable, and the torsional rigidity (side to side stiffness of the shank/sole) will save your ankles while side-hilling and climbing. If they don't fit well, look for a similar style of boot that does. Fit is paramount when it comes to boots.
Finally: If you are buying gear -- boots, raingear, clothing layers, down, gloves etc -- Don't get suckered into thinking you need to be wearing Kuiu, Sitka, First Lite etc to be a successful hunter. Quality boots, raingear, pack, and optics are more important than what color/pattern you wear. I've been down both the Kuiu and Sitka rabbit holes, both companies make some great products, however I have found that most mountaineering brands build equal or better quality products at a far more attractive price. Packs may be the exception to this, most hiking packs aren't built to carry 100lb+ loads. Outdoor Research is a good option if you are of the "I won't buy from X because they don't support hunting" mindset.