There are 3 packs each, or 45 cards. With 60 points, the average you will end up paying for each card will be 1 1/3. That means there will be a decent number of 0 point cards that you will need to take in order to get cards you want. 80 points would mean you could average just under 2 points per card.
Realistically, you only play around 20 cards anyway, plus lands and a few lucky "ditches", so you can probably afford to pay 3 points per cards that you intend to play and 4 or 5 if you really want the card. Just remember that every card you get for 4 or 5 points is less cards you can get for 3.
Given that there are only 5 players, there will probably be a decent number of playable "ditches", so I don't think 80 points is necessary. 60 should be fine. 80 points lets you pay 4 cards for anything that you intend to put in your deck and still probably have a buffer for bombs.
Ransac - Shuffling everything together should be fine. Since Melkor passed on Sisay's Ring, it decrements in value to 4 and a different 5-point card is turned over. Spidey has the option to take the new card for 5 points or the Ring for 4 points.
Consider it like a board with 6 slots labeled 0 through 5. When a card is removed from a slot, all higher-point cards shift down one and a new card is dealt into the 5 slot. Until all slots are filled, players can choose to pass instead (as Melkor did).