2. When you look at your stats, and lets say it says Focus 20 (+3), what does +3 mean? I get the 20, because that's where I allocated my points, but the +3 is...what exactly?
That's just your Bonuses. Your base stat (20) is determined by your regular stats, while your "bonuses" are determined by anything you have which would improve those stats - ie: Wearing a hood with Intelligence +1 would give you [20 (+1)] Intelligence, not [21]. (Although functionally, it's the same - it's just a different way of looking at things)
The Life you're currently in gives you a small bonus to a few stats, and often equipment that you wear provides a small bonus to stats as well.
And yeah, that bonus will stay so long as you're part of that Life or have that Item. You can see the bonuses each Life provides in your "Licences" menu - and likewise, pressing [X] on a piece of equipment will reveal what bonuses it grants.