The rent for a middle-tier quality apartment is cheaper in Cusco than Lima. If you are not sure about some of the things you've listed, maybe you should try and rent there for a little bit to test the waters and see if it works. Seems like kind of a big jump to purchase a place in Cusco without living there to see some of the costs/problems you may incur first hand.
I found the local common markets in Cusco to be cheaper and better than in most of Lima, especially the basics like chicken/eggs, and fresh fruits and vegetables. The fruit selection in Cusco is really amazing. More niche products grown in the Sierra like Chia seeds and Quinoa are also absurdly cheap. Cuy also
Outside of the plazaVea that's there, the local supermarkets are pretty lacking in Cusco compared to Lima, which is obviously understandable considering it's relative isolation. There's not a ton of selection and prices for some imported goods are even more expensive than in Lima.
Restaurants are generally cheaper, but often the quality or diversity of options that you'd find in Lima is lacking in Cusco. Notably as it's inland, outside of relatively good priced and quality trout, the seafood in Cusco is more expensive for the quality you receive.
I don't remember the kWh rate exactly but electricity seemed more expensive than in Lima. Having a gas heater would be a big cost savings I think.
Just my opinion here, but overall I'd say that cost of living is cheaper in Cusco than Lima with the biggest savings coming from cheaper rent and grocery shopping at the local markets. This comes with major caveats for sure, it could easily be more expensive depending on your lifestyle.