familiarity... observe.. and learn over time. They start to look different too.. color of calyx may change slightly.. pistils show color and coil up... The surface of the bud just looks different and you can see that spread out/progress. So, in general long hairs typically means more fattening to come...
Try to use multiple observances to determine harvest... trichomes, pistil coloration and density of buds - the last one you want to limit as much as possible as touching the plant is something to avoid as best possible. But, giving a mid level or lower bud a gentle squeeze isn't going to ruin much of anything.. just don't do it daily, lol.
you may need an extra few days to recognize the calyxes are fully plump at first, but that shouldn't hurt you at all as far as when to harvest.. plenty of time between fully fat and maturation of trichomes. It's a good time to start scoping trichomes daily.
New pistil growth could be environment (excess heat or light), could be waiting too long and it's over-ripened and starts to grow more, or could be just some odd genetic trait that particular plant displays...
'calyx' is just what those hairs pop out of.. it's a sex organ. It's function is to receive pollen. If you google image search, you'll see diagrams with some wildly different overall shape and size, so add 'marijuana' to that search string. just a little envelope with a pointy top and 2 hairs stickign out.
sugar leaves shouldn't die and shrivel up, but if a few do, it's not the end of the world, either... As long as it isn't widespread and prevalent, probably nothing to worry about as long as the plant can live long enough to harvest. Sugar leaves dying can also be a sign of trouble underneath - mold along stem. If controlling climate, should avoid that easily.
Use a trellis for support in future. It's much less effort than tying individual branches up for supoprt. You may not always need it, but you'll sure appreciate not dealing with all those yoyos and individual attention and effort to every branch. Simply spread out the branches and they'll lean on the trellis as needed. Again, familiarity of what you expect helps alot with placement of the trellis. I want no more than the last 1/3rd of vertical growth above the trellis.. 6-8" and it won't flop over. If you don't know what to expect, may need to raise or lower the trellis to work effectively if it overgrows or undergrows compared to expectation when you initially placed the trellis.
big buds is mostly gentics, but also impacted by how many bud sites are sharing dominance. Can never cause donky dicks if the genetics don't allow it. A single primary cola will result in much larger buds on that branch than several 'equal' colas distributed across a canopy -- yield is not impacted much by this, but risk of pathogens is... good to find that happy zone of bud size that gives high proportion of non-larfy buds without being so dense you worry about bud rot. 2-3 vertical, level branches is all you need per square foot to maximize yield. More just results in smaller buds of same total mass, ceteris paribus.
On top of all that... personal preferences ... nobody can tell you exactly when to harvest. You may prefer more or less ripe buds. You'll have to experiment and try new thigns to figure out exactly how you want to do it. Even methods are impacted by your personal needs... maybe you want 1/3rd larf for bubble hash or edibles or other extracts etc. Maybe you want to take clones, so that requires a long enough vege phase to provide cuttings.. so smaller, faster-finishing plants are not an option.
When discusing individual parts of growing, we speak of what is optimal, but what is optimal may not always fit what is needed. E.g. i could save a two weeks of vege phase growing a greater number of smaller plants while filling same area, but then i can't take clones for breeding cycles. I want to err on having a bit more larf, because it feeds my bubble hash production, so that is impacting how i train and prune... something that will take a couple grow cycles to hammer out a consistent procedure for a consistent outcome i can depend upon.
Easier to adjust than to learn from scratch, but it's fundamentally the same process.