Keep your credit cards seperate. In my opinion, it's better for you in the long run. In fact, other then mortgages and things related to the home, try to keep your car loans seperate also (except maybe the 1st one). And whats good for you isn't just about your credit scores.
Have you had that $500 CL card for very long? If so, try asking for a CLI.
Your scores are not that bad. You should be able to qualify for a higher CL somewhere unless you have low income, a very high debt to income level, or no credit history, or some very recent negatives. In fact, I got higher CLs from cards when I was a poor college student back in the early 90's when $500 was worth more. A $500 CL should be for people under 600 or no history or no income. Unless you are going to try to buy a house in the next 6months, I'd apply for a credit card from another bank that gives out credit a little easier.
Current FICO8: EQ:782, TU:754, EX:767 | 1x 30 day late 6yrs ago
AAoA: 10 years;
AAoOA: 13 months;
Credit Length: 21 years
INQ Eq: 3 / Tu: 5 (4 for auto) / Ex: 9 (5 for auto)