I see that your question was originally posted in Mental Health, and has been dual categorized to Health. I am educated in both areas, but if your main concern is your heart condition, then it will be best for you to respond to doctor Brims.
Regarding your intrusive thoughts and worries about your family, there is support for you, and it is very important that you get this support.
There are caregiver support groups,as well as CODA groups (CODA is a support organization for those with family members with drug problems and besides giving you a place to discuss the problems, there is support, and you are given skills to learn the best way to deal with family member's addictions.
For right at the moment, I can give you a link that will provide some ideas on how to deal with caregiver burden, but also, if you would like to write back with the area of Australia that you reside, I could look for specific support groups for you.
This is the home page of a website that has info on helping those with addictions, prevention of suicide, caregivers stress, and more. Click on this LINK
For information on cargiving stress in particular, see this LINK
I also did find the page for CODA Australia. You can go here to look for support groups in your area. You will find people here with similar issues as you. CODA
Now, again, as I mentioned earlier, if your main concern is your heart or your medical condition, please respond to Dr Brims.
IF you would like more info or have questions for me, please do reply. If you are satisfied with my answer please do rate me positively, as this is the only way I receive the pay for my work.
If you would like further help though with your emotional stress issues, I'll be standing by to assist you. Again, please do not rate us until you have had your question answered to your satisfaction.