Sounds like you had an interesting introduction to the pleasures of the the Mirage Drive equipped kayak
...these, unlike a paddle kayak, can easily take pretty much anyone several miles off shore as you no doubt appreciate! The well equipped, and conservative will be the ones who always make it back to shore again.
FWIW there are several threads on these forums about safety gear which are worth looking at. It is also worth reading the book Total Loss (I think that's what it is called) which describes various losses of small boats at sea in detail and makes recommendations re safety equipment - it is a right rivetting read on its own merits and some (though not all) of its recommendations translate directly to kayaks. The point is that we each have our own unique risk profile and these, and other, sources provide useful suggestions as to how others equip themselves for their trips (FWIW I always take baler, drive spares & tools, radio, GPS and I ALWAYS WEAR my lifejacket... and I will shortly be buying a PLB for use on kayak trips and in the bush).
The wearing a lifejacket message is a case in point. It is a legal requirement in NZ that there must be a lifejacket for every person onboard but you don't actually have to be wearing them. A Coastguard once made the point to me in the following way: it is no use just taking them with you - how much sympathy are you going to get if they say of your drowning (or that of any of your crew) "they pulled his body from the sea - he had a lifejacket but he wasn't wearing it when he fell overboard". And the coastguard in NZ regularly has to make this kind of report!
Like you I am surprised that your PA filled with so much water after you capsized but if you had had a baler (in my case a large carwash sponge) you would have been able to use it (one of the messages I remember from Total Loss - I think - is that a frightened man with a bucket cam move more water from a boat than any sort of bilge pump - nearly!). I suffered a crack in the hull of my Adventure a couple of years ago and ended up having to bale/pedal/bale/pedal to get back safely - in these circumstances a baler is a lifesaver.
You also understand why everything on deck needs to be clipped to your boat - I have just revisited this very lesson myself this weekend if you have a look at one of the other posts on this site! It is also worth attaching all safety equipment that you keep inside the hull to a point so that it will not slide out of reach inside the hull - on the Adventure the rim of the centre hatch has holes drilled in it to which you can tie fishing line leashes to attach your safety kit to - then you know that you will be able to get your hands on the things you really need in an emergency.
Hope this helps and try not to get put off