Although  metformin is typically thought of as a first line therapy for those  newly diagnosed patients with type 2 diabetes, it is not always  appropriate for use. In patients with moderate to severe renal  dysfunction, one would want to use another oral agent. The FDA  recommends monitoring the glomerular filtration rate (GFR) and if the  GFR is below 30mL/min, they should not be put on metformin  (Aschenbrenner, 2016). If the patient has a GFR between 30-45, the  recommendation is to use a reduced dose of metformin accompanied with  SGLT2 inhibitor, which reduces risks for both chronic kidney disease and  CVD (Naveenthan et al, 2021). It is recommended to monitor the eGFR at  least annually or more often in older patients so as to avoid lactic  acidosis. Additinally, the patient should be counseled on diet and  weight loss along with pharmaceutical therapy. (Aschenbrenner, 2016;  Naveenthan et al. 2021). 
Jardiance  and Invokana have been shown to reduce cardiovascular death. In a  random retrospective study which was described in the New England  Journal of Medicine, empagliflozin was found to decrease inicidence of  cardiovascular death or worsening heart failure by 25%, as well as a  slower kidney function decline. (Slomskik 2020). 
Evidence  based therapy would involve talking to the patients and getting a good  sense of their lifestyle and their ability to change behavior and diet  as well as conform to medical recommendations. Utilizing research and  evidence-based research to determine the best route for the individual  patient rather than just prescribing medication based on training.  (Makam et al, 2017). 
It  appears that the patient has developed hypothyroidism as an adverse  effect of his amiodarone use. Amiodarone tents to concentrate in tissues  including the thyroid gland, which is why it affects it specifically.  The recommendation would be to switch the patient to another  anti-arrythmic medication such as dronedarone which would provide the  anti-arrhythmic effects without the adverse affect on the thyroid  (Narayana et al, 2011). Additionally, I would recheck the thyroid  function in 4-6 weeks to ensure that the thyroid dysfunction was indeed  linked to the amiodarone use and not a pre-existing disorder that was  missed.
Aschenbrenner, D. (2016). The FDA revises restrictions on metformin use in kidney impairment. American Journal of Nursing, 116(8), 22-23.
Makam,  A. N. & Nguyen, O. K. (2017). An evidence-based medicine approach  to antihyperglycemic therapy in diabetes mellitus to overcome  overtreatment. Circulation, 135(2), 180-195. https://doi-org.wilkes.idm.oclc.org/10.1161/CIRCULATIONAHA.116.022622
Narayana, S. K., Woods, D. R., & Boos, C. J. (2011). Management of amiodarone-related thyroid problems. Therapeutic Advances in Endocrinology and Metabolism, 2(3), 115-126. Doi: 10.1177/2042018811398516
Navaneethan,  S.,  Zoungas, S., Caramori, M. L., Chan, J., Heerspink, H., Hurst, C.,   &Liew, A. et al. (2021). Diabetes management in chronic kidney  disease: synopsis of the 2020 KDIGO Clinical Practice Guideline. Annals of Internal Medicine, 174(3), 385-394. Doi: 10.7326/M20-5938
Slomski, A. (2020). Empagliflozin cuts cardiovascular deaths in advanced heart failure. JAMA, 324(24), 2476. DOI: 10.1001/jama.2020.24667