You can put Lost Souls in sites to prevent Heroes rescuing them. For example, if your only Lost Soul is in a blue site, your opponent can only rescue that soul with a blue Hero. There are abilities that give Heroes access to sites they normally couldn't though and using sites to guard souls has been almost entirely phased out as a viable strategy. Any sites used today are because of their special ability, which on rainbow sites activates when you add the site to battle (which you can do any time during a rescue) and on non-rainbow sites activates when the site is put in your territory.
You can only make one rescue attempt per turn unless a special ability specifically allows otherwise.
Yes you can. There is no limit to the number of souls that can be rescued in one turn (unless a card specifies otherwise). The limit is on the number of rescue attempts that can be made.
The dominant Falling Away from the Women set effectively "un-rescues" a soul.
As long as you are following the deck building restrictions that is a thing you can do but it would be terrible since you would never draw all your best cards. A smaller deck is almost always straight up better than a larger one since if you're over 50, you can simply cut the least good cards from the deck until you are down to 50, making the average card in your deck better. There have been decks made in the past that had strategic reasons to use more than the minimum number of cards but I don't know of any good decks that used the max (in Type 1 anyway, there may have been some wonky Type 2 strat long ago that I don't know about).
The rulebook is unfortunately pretty outdated and missing lots of information. There is also the Redemption Exegesis Guide (REG):
http://landofredemption.com/wp-content/uploads/2017/06/REG_PDF_4.1.2.pdf It is supposed to be an exhaustive catalog of game mechanics but it is also a WIP. There is a major update coming to the REG and rulebook any time now.
With only the current versions of the REG and rulebook, it's very likely you'll miss a lot of information. When I taught myself to play years ago I had a LOT of misconceptions about how the game was played which I have had to unlearn over time and by playing with others. If you have any further questions about the game at all don't hesitate to ask.
