Quite a few questions about Echium appear on here, so you might like to look them up using the search facility. I understanding is that they are not very hardy and once the top is damaged, it cannot then be cut off and resprout from lower down, as it just has the one shoot at the top.

I would leave it for now and see if it recovers later in the year. Some shrubs have been known to wait until July to regrow after a very hard winter - it depends on how long you are prepared to wait but I would give it until at least May

Echiums (wildprettii and related types) are very tender and they grow most easily in places like the Scilly Isles and their natural home, the Canaries, Madeira etc.
I have grown them often over the years but always lost them, even in an unheated greenhouse, before their second year when the flowers should have come.
As yours is four years old it may have more powers of recovery, but I very much doubt it after all that snow and freezing temperatures.
Don't do anything to it other than protect what's left, and see whether it makes any growth at all when the weather turns warm. Often severely frozen plants only start to regrow in June or even July, as we had a guava that was knocked right back to the base of the stem. By the end of the summer it had almost regrown into its previous size.