I found this site before when i was looking for the same, you can try it and you will find some comments at the end of ppl who do it and it worked for them , i didn't try personaly until now i am ok with teamviewer 800*600 
Here the site: https://rumorscity.com/2013/12/06/how-to-create-dummy-plugs-for-your-graphics-cards/
Edit: maybe your problem isn't the dummy plug because i have many rx470 rigs working without dummy or monitor just teamview with 800*600 , there is some parameters in windows you have to set them to let your rig work stable like disable action center , windows defender , windows update , maintenance , sleep time , power plans ...you have to check the above list or your rig will not work stable.
Here the site: https://rumorscity.com/2013/12/06/how-to-create-dummy-plugs-for-your-graphics-cards/
Edit: maybe your problem isn't the dummy plug because i have many rx470 rigs working without dummy or monitor just teamview with 800*600 , there is some parameters in windows you have to set them to let your rig work stable like disable action center , windows defender , windows update , maintenance , sleep time , power plans ...you have to check the above list or your rig will not work stable.
Do you use trixx for fans settings?
