Hi,
No, it is not possible to dynamically create Test Items during runtime in TestComplete.
Also I am not aware that TestComplete supports partial execution of Test Items tree during parallel execution. (I.e. when first test box starts first test item, second test box starts second test item and then test box picks next test item from the execution plan when it (test box) is done with execution of its test item -- this is not supported.)
The idea that I have of top of my head is to add some logic to your framework, so that depending on the number of available test boxes, each of them picked up only its portion of enabled tests.
E.g., considering two test boxes available, the first box would execute only odd tests and the second box would execute only even tests out of common list of enabled tests.