It sounds about right.  Of course, your client's filing status and actual deductions allowed on the return will all make a difference.

Did a quick mock up with your numbers and my Line 18 is adjusted automatically, as with Line 1a.  The assumption is that your client is single and has only S/D.  If you're certain your Line 18 is not adjusted, you may want to check your input and overrides to make sure nothing is amiss.

Just as a note, the foreign tax is not being "reduced" to $5k.  It is merely the credit that is being "limited", which is exactly the intention of the regs.