Can hydrocortisone make jock itch or fungal infection worse? if so, how much worse?

Yes: Hydrocortisone stunts your skins immune response that causes the redness. For this reason the hc might make the jock itch look improved at first. But the condition is caused by a fungus; so if you impair your skin's immunity, the fungus will grow more rapidly, eventually making the rash worse. When in doubt, mix the hc cream with an anti fungal cream, but not for more than 2 weeks.

Use antifungal: Theoretically, but you can use it with an anti fungal. Try using some micatin (miconazole) with it.