You have it fairly right. A bit of backwinding the main is ok. If you keep the jib in tight that is your main source of power.
However the boat will sail better not heavily heeled.
Say the wind was actually 20 that gives you close to 25 upwind. Gusts usually add up to 50%.
Your sail plan in standard sails ie jib and full main is optimised for about 15-17 knots. The force is windspeed squared ie say 256/625 =.4. That is you need 40% of the sail area, assuming you cater for gusts in other ways.
Essentially you were overcanvassed made worse by sails that are probably blown out ie too full.
You are correct that main alone going to windward will give you weather helm. Although it is influenced by hull shape it is mainly due to the balance of sail area fore and aft of the centre of lateral resistance ie the turning point of the hull.
You may be able to get the sails recut but the cloth is probably stretched so at best they would be cruising spares.
You probably need a wind gauge so you know the windspeed fairly accurately.