I still feel that way some days to be honest. I thin k i have dealt with it all and then something will catch me out and i feel sad and wish things were different. But not in the way it sounds i never wish DD was different i just wish i could take away all the things that are hard for her, all the surgeries she has been through, all the injections and blood draws etc, and how hard learning the basics of growing up has been for her. There are upsides to that too though, every milestone she hits is a much bigger deal for us than it is for other parents, becasue she has had to work so hard to get there. Its different for everyone though, i have a friend whose twin boys also have a conditon and she is absoluty the most positive person ive ever met, she regrets nothing about her life with the boys and wouldnt change a thing. It just takes time to get there for everyone and you are still very new to this new life.
There is a short poem you should google. Its called 'Welcome to Holland' Some people i know have found it patronising to special needs parents but the first time i read it was just exactly the right moment for me. And from the way you are talking i think it might be helpful for you to read. I found it helpful for me in adjusting my view on how things had changed for us.
As far as your DH resenting you goes I'm sure it will be fine, I have found somedays my husband is actually more accepting of DD's extra needs than i am. He as a very typical man approach, he doesnt wish she was different ecause she is just robyn and she cant help how she is so we just get on with it.
With the cardiologist i will say dont expect them to over explain things, all heart doctors are fantastic with hearts but less good with actual people. They tend to keep descriptions short and technical. Take a notepad with any questions you want answered on it, write things down to google later and if you dont understand something push them to explain it. Also ask if your local hospital has a cardiac liasion service. (ours doesnt) however the local childrens hospital does so we phoen them if we have questions and they are always happy to explain terminology or procedures etc. Not sure where you are exactly but there is bound to be somewhere nearby ish that will have a liasion dept.