Thank you so much for sharing your experiences with us karolinka. I think you've touched on so many important points in your post that deserve to be fleshed out.
To the outside world, your survival of cancer is viewed as a perseverance and a resiliency; but there are so many aspects of your identity lost along the way that it's so difficult to be that same person again. Creating that new normal that you speak of often means dealing with the disenfranchised grief you experience from society and their perception of your strength. Then compound that loss of identity with the loss of your father and the adjustment to life after cancer seems even more daunting.
I think you are doing the right things for yourself to begin to heal and form your new identity. You're pursuing support in multiple forms including this forum. You're being realistic with your ability to cope with getting back to work and understanding that you might need more time for introspection.
The two books that I have become quite fond of that I often recommend to people are:
Being Mortal by Atul Gawande - https://www.amazon.ca/Being-Mortal-Medicine-What-Matters/dp/0805095152
and
When Breath Becomes Air by Paul Kalanithi - https://www.amazon.ca/When-Breath-Becomes-Paul-Kalanithi/dp/081298840X/ref=pd_lpo_sbs_14_img_0?_encoding=UTF8&psc=1&refRID=1JHGD6CBAGG06D2JBPRF
Two fairly quick reads by remarkable physicians that I hope you enjoy.
Also, if you're looking for other mediums of support; I would recommend checking out MyGrief.ca. It is an online, modular program that allows you to work through grief of any kind in your own unique way.
Thanks again for sharing with us karolinka and welcome to the forum!