desperately, I understand your use of the term 'walking on eggshells'. That sums up my life with dd 5.7 and ds 2.7, when they were younger.
I saw real improvement with dd, once she turned 3. At 5, she is still moany, but as they get older, you have more tools at your disposal, like reasoning, humour (if you have the energy for that), peer pressure.
The knee-jerk crying after waking from sleep will definitely go away, probably quite soon. From your name, is your ds2 a bad sleeper?
Ds is still quite whingey at 2.7 and frequently kicks off, but he is much better now. It is worse when he is under the weather, eg like teething or illness.
If it gets too much, I tell him that if he wants to tantrum, he can go to a spot on the carpet and flail and scream as much as he wants. But I will go off and do my own thing. It might not work to calm the demons, but at least you can get stuff done. Sometimes, nothing you do will make him happy and he just needs to let off steam. Then, when he is ready to come back to me, he is happy as a clam.
How do I cope? Nursery. Both dcs were much less clingy and more independent at nursery. I think they are both quite sociable, hence the turning to you to tell you that the world is not right or they don't feel right - translates into whingeyness.
Nursery was great because there is a lot of activity and friends and they forget to fuss. They actually played by themselves there. Unheard of for them to do at home, at age 2 at least.
It will get easier, promise.