Answer: Most container and cartons in practice can be computed. According to Wikepedia, container the longest is 17.1m, the widest 2.6m, the highest 3.2m, which are used as space limit the maximum (by mm). The carton size limit the minimum used is 250mm long, 100mm wide and 100mm high.

Answer: The algorithm is not taking corner parts into account. You'd check whether the loading plan can accommodate corner parts, or you need to use smaller space size instead to compute.

Answer: That could happen in some cases. When space is big and carton is small, the loading pattern can take a huge number of variations and the algorithm only search through a portion of them, then it may happen that an even better solution did not get found. The Professional Edition of SmartPacker search deeper and sometimes find better ones than did Basic Edition.