In our blood, Iron is used in our blood cells to help oxygenate our blood. Iron is an important component in hemoglobin, which is what carries oxygen from our lungs to the rest of our bodies. BUT, there are other types of blood transportation molecules found. To see those, I would look at this question and answer: Other blood colors
Now as for better viral resistance, that comes directly from actually having a virus (that's why we have vaccines). When a virus enters our body, it has on the outside of it something called Antigens. Antigens are the part of the virus that triggers an immune response. After a body has a virus, it creates antibodies, which interlock fit into an antigen sort of like a lock and key. Antibodies help your body fight a virus faster and easier the next time you come in contact with it. To have better viral immunity, while genetics can play a part in it, a person has to develop antibodies against the virus.
In reference to larger lungs, this has been discovered in people who have adapted to living in high altitudes. Larger lungs help collect more oxygen from thinner air, which helps people stay alive. https://www2.palomar.edu/anthro/adapt/adapt_3.htm
As for CRISPR, CRISPR is a gene-editing tool that we still are researching. The basis for it is replacing small portions of DNA to help fix problems. As gene editing and the science behind it is still being learned, there are a lot of unknowns. We do not fully know how gene editing could affect a person's genome in the long run. Additionally, the ethics of it are questionable and can lead into eugenics, which is a HIGHLY discussed, questioned, and often disliked concept (editing for human perfection). https://www.livescience.com/58790-crispr-explained.html
The science behind what you're asking for isn't completely there, but it is to a certain degree.