Ryanair have a good reputation for safety, and they generally do a good job of shifting thousands of people round Europe every day. Their customer service is what's earned them a poor reputation, but my last (and only) recent experience with dealing with 'them' by on-line chat was very positive. I have found their flight crews to be usually OK, friendly and chatty, certainly no more rude than of Finnair, British Airways, Japan Airlines, Lufthnasa, KLM, etc.
Like it or not, Ryanair is a success story. As Michael O'Leary puts it: "Our planes are full of people who hate us!" There are a couple of books about Ryanair's history, where a chap travels to various destinations around Europe - I enjoyed reading them (around 15 years old now?) and would recommend them. Of course, dated now.
That's the size for the small bag. You have been told. It's ridiculously small, I know. Used to be bigger. A bigger 'bag' ('small rucksack/daypack') will also easily fit under the seat i front of you, but it all depends who's at the gate/check-in counter. A couple of years ago I asked the Ryanair lass (at a queue for another departure than mine) what she thought of the size of my daypack (it was a bit over in all directions) and she said "Does it fit under the seat? If so, that's OK." I have had no problems with Ryanair 'measuring me up', ever. You can put underpants and socks in your jacket pockets, and stand at the end of the queue so that when you get to the gate they're too rushed to bother to check anymore.
If two of you, why not have one item that goes in the hold? A rucksack is much easier to carry than a silly suitcase. OK, it may cost you 45 Euros (one way) but you've already saved 400 Euros on the ticket price compared to a 'major' airline!
Food? Make your own/buy at the airport - but remember this will also count as 'luggage'! You could eat before the gate. In-flight entertainment? Read something, or take paper & pen and write your memoirs. I like to look out of the window on planes; I still think it's amazing to be zooming along at 900-1200 kilometres/hour 13-14 kilometres high - most people simply don't comprehend/appreciate this. When you have driven he same distance by car (as I have) then 2.5 hours certainly beats 2.5 days!