Deer resistance really depends on the deer and how hungry it is. If you have a dense deer population, they will eat almost anything to stay alive. That said, lavender, with its intense smell, is one of the last things a deer will sample.

You lavender will need you to water it regularly this season. It needs water to get established. After this year, it probably will be fine on its own. You should not have to fertilize it. Lavender is native to Mediterranean areas and has evolved for lean, well drained soil, with little water in the summer. 

I would not cut it down in winter. I cut off the old growth in early spring, as soon as I see buds appear near the crown of the plant (the base or trunk). You do not have to prune lavender at all, but pruning it short--cutting it back to just a few inches tall--keeps it tidy and a nice mound shape.  A lot of sources say to prune in August or September. I believe that the Romeo Lavender Farm does that. However, I also read that lavender is prone to winter die back if pruned in fall. I have pruned lavender in early spring, before it flushes a lot of new growth, and had good success with it.

Lavender is often a short-lived perennial for us because of our climate. Most people are lucky to get 5 years out of a plant. 

Lindsey K. Kerr, MS, MHP (she, her, hers)
Consumer Horticulture Educator
Michigan State University Extension