Hi there, sorry for the inconvenience. Regarding the inventory; its not a bug, every time you die you do lose everything in your inventory.
Best way to avoid losing everything is to craft storage spaces for items/ materials and store whatever you collect/loot.
As for the Co-op effecting the computer temperature; its because (If you are the host) you run all the AI on your computer then share the states with the other players, I do plan to optimize it, as for now a solution to this issue is to host a private multiplayer server instead of CO-OP if you don't plan to interact with the AI.
Thank you very much for the report/feedback!
Will do my best to improve and solve all issues.
Best regards.