The $1,500 is probably the correct amount of credit in your situation. The Child and Dependent Care Credit is based on expenses that cannot exceed your earned income.
For married couples, it is based on whichever spouse has the lowest income. According to the IRS, a full-time student is treated as having an income of $250 per month that the taxpayer is a student. Since your spouse also had some earned income, for each month they would choose the greater of their earned income for the month or the $250 for being a full-time student.
When you enter the information for the Child and Dependent Care Credit, it will ask how many months your spouse was a full-time student and if there were any months where their earned income exceeded the $250. For example, if your spouse was a full-time student for 9 months and during the summer had a job where they earned all $926 dollars, then the credit would be based on $250 x 9 + $926 = $3,176.
Based on your spouse being a full-time student all year and never having a month where their earned income exceeds $250, the qualifying expenses for your Child and Dependent Care Credit is limited by your spouse's total income of $3,000. At your income level, you receive 50% of the expenses as a credit for the $1,500 that is reported on your tax return.
