Howard. All trees are dormant at -5F. the question is can a lemon tree ever adjust to those temperature and survive. That answer is also NO. You can increase its cold tolerance by slow growth and early hardening over caused by clayish soil, but not to the degree you need. You will only get a lemon down to z6b by mutations that survive the cold. In time you may get the lucky seed. The more seeds you plant the more chances you have. Right now the best you can do is a Harvey lemon grafted to Flying dragon rootstock. The FD rootstock produces better lemons than the lemons own roots could do and adds 5F colder tolerance.

 But I will need to wait until I get to Washington D.C first before I get them   so I can get better  access to them first

Howard. These are articles on how to get more from a cirrus tree. While this was done on kumquats, the same process could be done on lemons to achieve your needs. https://www.researchgate.net/publication/335895525_The_Confirmation_of_a_Ploidy_Periclinal_Chimera_of_the_Meiwa_Kumquat_Fortunella_crassifolia_Swingle_Induced_by_Colchicine_Treatment_to_Nucellar_Embryos_and_Its_Morphological_Characteristics https://www.sciencedirect.com/science/article/abs/pii/S0304423818307106

It would be a lot eisier to build a small green house over a deap well planted harvey lemon on cold hardy rootstock such as flying dragon.