I work in midwifery and we see lots of babies with prolonged jaundice, especially if they're exclusively BF. We recommend a bilirubin and liver function blood test at around 3 weeks if a baby is still visibly jaundiced, but the hospital down the road (a different Trust) does this at 2 weeks. Some babies will still have raised levels of bilirubin at 3+ weeks but if the baby is otherwise well and above birthweight, the doctors tend to leave well alone and "wait and see", usually offering a final blood test a little later on (6-8 weeks). It's very rare that a baby will be readmitted after their light therapy has finished, the final blood tests are just to ensure that nothing has been missed.
If your baby has had light therapy, and afterwards has had 2x bilirubin tests where the level is below the treatment line and falling, your baby will be discharged. Again, they would repeat the blood tests at 3+ weeks, just to make sure that all is well.
I know that these tests are horrible, and it's very disheartening to have to keep going back to hospital, but we are saving many more babies from serious illness with this approach. We do feel your pain though, having to take several heelprick tests over the course of 2 or 3 days, is no fun for us either, especially with those poor babies that just don't bleed much, and we have to prick them 3 or 4 times in the same foot, just to get a tiny bottle of blood
The "3 hourly" feeds advice causes so much confusion. If your baby is very jaundiced, it can make them sleepy and lethargic, they can sleep through their feed times and can end up becoming weaker, and will lose more weight and can get dehydrated. If they are older than a week, gaining weight well, are alert and active, and you know that they are having decent feeds, you don't have to wake them on the clock at 3 hourly intervals. I wouldn't let them sleep for much longer than 4 hours when under 3 weeks old, but sometimes, waking them up before they're ready, is just counterproductive, they're not hungry, and they're cross because they're still tired.
Nipple confusion is very common if you've had to bottle-feed your baby in the early days. There is help out there if you want to continue to BF, although in some areas, you may have to hunt it down.
. La Leche league, BF Facebook groups, and your HV should be able to help, and remember, breastfeeding is an ongoing process, just because something isn't going right today, doesn't mean that it can't be fixed sooner or later. It's a bit like learning to drive, you can't get everything right first time!