In regards to your credit card. The general rule is to allow no more than 9% of the total available limit report. So for a $1K card you should never let more than $90-99 report. When you have more than 1 CC and you have no debt at all, you score can actually go down because then you're not using credit at all, so there's no way to know if you're responsible with it. With only 1 card, I'm not sure if your score would go up or down.
You may want to go into the credit card forum and read up on credit cards. Having a store card in addition to a major brand card, Visa, Mastercard, etc, can actually help improve your score. However, since you want to get a home soon, I would not reccomend applying for any additional cards, regardless of the possible score benefit as many lenders do not want to see any new accounts.
Your scores right now will qualify you for FHA, but most lenders like to see at least 2 years at the same job, or in the same field. An exception to this is if you just graduated from college.
Your file also seems short, only 7 months, however you do have a substantial down payment, which at times can help overcome short coming.
I would caution you not to use your enitre inheritance and $16K that you have saved on your own for your down payment. Even though FHA does not require reserves, you never know what you may need to buy for your new home in repairs/remodeling, etc. And you should definitely have a good cushion in your accounts for those unexpected expenses.
Good for you for buyin a house at your age.
You'll probably get more definite responses from Shane or Dallas, but that's what I know.
