always have portals. Back home to repair takes seconds, and you can rest up again and drop off all the rocks and wolf parts and such that you picked up during your adventure. When its all said and done, grab all the ore and waddle down the mountain. Drop it, stamina comes back, pick it back up... you can go a long long way on full stam food doing this, and get it to your boat. The game does not distinguish between 1 pound over the limit and 100000 pounds over the limit.. :)
for the boat, if you got more than it will hold, bust a cart and kick the little boxes onboard.
sliding does not count against stamina. There is an art to sliding down a mountain for 'free' when under a heavy load.