Lethe, you made a good point about Angel's age and because he was in a hell dimension he should probably be around 350 years old. But according to the series, time in a hell dimension obviously moves a lot faster than our time here. This can make things complicated.
In BTVS- season 3, from Angel's point of view he was gone for hundreds of years, but for everyone else on earth it was only a few months. His age would really depend on who's point of view you're talking about (Angel's or everyone else's) If you were to say he was 350 something years old, you'd have to go from earth years, to hell years, then back to earth. Which is kind of complicated. So when measuring Angel's age, it'd probably be best to say he's (some thousands) of hell-years old or around 250 "normal" years old.(stick with one demension's time)
The same thing with Connor's age, he could either be a teenager or however long he's been around for everyone else.
(and who said time can be confusing? 😉 )