Some rough ideas from chatting to new cadets (not in the order of your points I'm afraid)
1. Expect around 5 months from joining to first pay check.
2. You will get almost no choice over your initial base unless you are keen to live in one of the less popular bases - Poland, Greece, S Italy mainly. Base transfers happen mainly in February and September (start and end of the summer season) and are somewhat of a lottery. The wait depends on how big the base you want to move to is and how popular it is.
3. You will be offered a contract with Storm, and the rates of pay are pretty rubbish. The hourly rate is lower than was offered when I started nearly 5 years ago - expect around €35/hr during line training and maybe €50/hr once released.
4. Hours flown are variable. Make sure you save money during good months to even things out and account for your month off. 700-750 hours/year is a reasonable guess to do your figures on. Money for hours more than that should be considered a bonus.
5. Once you get your contract you will see the pay rates. The steps were previously at 500 and 1500 hours in type. There is no SFO as such but you pick up a 3rd stripe 12 months after your second line check.
6. Tax and social insurance is an unholy mess. In the UK, you now pay it all in the UK. You will need a certificate showing where you pay your social taxes - your accountants will advise you on this. When I was based on the continent, I paid social insurance where I was based and tax in Ireland.
7. I have enjoyed my time at Ryanair in terms of the flying, my colleagues and the friends I've made. It can allow you to work close to your home wherever you are in Europe. However, bases may open, close, expand or contract at the company's whim depending on industrial relations and commercial considerations so it doesn't pay to get too settled if you are at a small base.
8. Ryanair works best for Captains on Ryanair contracts with a family home close to their assigned base. If you are in the right hand seat, command upgrade will involve at last a year sent to the back and beyond, probably supporting two households if you are married or in a relationship on a reduced salary and can be very difficult. Have an exit plan if that isn't for you. Remember how you feel now, probably single, looking for your first job is not how it's always going to be.
Best of luck.