How much does one have to pull on the eyelids for it to cause significant sagging not due to age?

HiYou pose an interesting question. Pulling the skin and heating it with brow treatments such as waxing, plucking and electrolysis can over time, impact on the quality of the skin. The technique to prevent damage with plucking is to hold the skin taught and this generally makes the procedure more comfortable. I would suspect the bleeding is more due to thick hair follicles breaking out of the skin. A face to face consultation would be needed to see how heavy your lids are and whether this is coming from excess skin in the lids or a drop in your eyebrows or both. One should also look at pictures of you in your younger years and take a full assessment of your facial skin to look for other causes such as environmental and lifestyle accelerated ageing.