Spice: feel free to use as much or as little jalapeno as you want. To make it even spicier, leave the membrane and seeds in the jalapeno. To make it less spicy, remove the seeds and membrane from the jalapeno before use.
Taste: everyone's salt preferences are different so definitely taste after it simmers a bit and add more salt, per your own taste.
Storage: store leftovers in an airtight container in the refrigerator for up to 5 days.