It's a split backstay with a line and single block to control it. It was as tight as a good pull on it could make it. No clue about the forestay.
Old. No idea how old. No boltrope.
No clue. What should it be, and why is it critical? A racer or technical sailor I am not.
Your boat if properly set up should have a very neutral helm, even when substantially heeled.
That you described heavy weather helm Id be suspicious that the forestay was too slack and greatly sagged off to leeward. This will cause a skid to leeward and is erroneously thought/felt to be weather helm. Next time out in the higher windranges, look to see if the wake coming off the stern is 'straight back', if not the boat is skidding and the usual cause is a too slack forestay. A too slack forestay causes the luff of the jib to be positioned FAR off of the centerline and the draft position goes 'way' aft, powers up the jib and unecessarily hooks the jib leech to weather.
The boltrope is a 3 strand dacron rope inside a sleeve at the luff of a mainsail. Most common dacron mainsails have them ... and the problem is they SHRINK over time and cause the sail to become 'baggy', draft aft, overdrafted and the leech unnecessarily hooked to weather, all causing: .... aggressive heel, tender boat, and LOTS of 'weather helm'. The angle that the 'top' of your boom makes with the mast when 'correctly' raised (proper halyard tension) should be ~89 degrees. If you havent applied sufficient halyard strain or the boltrope has significantly shrunken that angle will be much more than 90 degrees (aft of boom will be noticeably LOWER than the gooseneck).
Next time out in 15+kts. and the boat seems to have weather helm, increase the halyard tension until the helm becomes 'dead fish' neutral when beating ... the boat will sail in a STRAIGHT LINE with no weather helm and no lee helm, then 'back off' slightly with the halyard tension until the boat s-l-o-w-l-y heads up to weather with your hands off the tiller. That should correct a lot of your 'weather helm' problems. I contend that probably 95% of all non-racing sailors dont properly raise a boltroped sail ... and that all by itself causes 'most' of the weather helm problems they experience.
Of course if that forestay is too loose and is sagging off to leeward, the boat will skid off to leeward and the helm will 'feel' like weather helm ... but a skid will be differentiated by the wake coming off the stern at a noticeably large angle (greater than ~5 degrees) ... not coming out essentially 'straight back'.
If the boltrope has severely shrunken (aged) and requires immense halyard pressure to get the sail tack angle to be ~90 deg., then take the sail to a sailmaker to get the boltrope 'eased'. Easy to check the tack angle on a windless day at the dock. Just use a large square sheet of cardboard.
hope this helps.