Who was going to hoist you up there??? is your wife willing to go up? If so it would be much easier for you to hoist her up than vice versa.
We usually take the halyard and re-lead it to a primary sheet winch for more power - still it's a bit of a chore esp if the 'liftee' is unable to assist by pulling on a spare line and/or shinnying up the mast a bit on their own.
Also good idea to have a second line connected as a backup, - don't let it get too slack along the way - and remember to ease it as well when coming down.
With help and caution, often the halyard can be led to an anchor windlass for power assist.
As far as the chair/seat itself goes, not sure what to say about that.. I'd expect a decent safety factor and that the language in the manual is lawyer-ese CYA... but of course YMMV and I'd hate to be the one to 'discover' the real limitation.