>>327758
>Speaking of, should I incorporate cardio to build stamina, or will this do just fine?
That's up to you.
>Also, how important is good form for a push up?
Fairly important.
>I realized I arch my back whenever I do them
Which is not what you want to do.
>I think I plant my hands too high up
Not super ultra mega important, you just end up training different muscle groups.
If you want a standard of sorts, when the Spanish armed forces have their recruits do pushups, they have them position their hands so that when they're in the downward position of the pushup, their thumbs are touching their nipples.