Hi, The anode is the most important thing to keeping heaters going. It seems the softener ate up the anode, but I’m a bit surprised that you had a lot of sediment also, as the softener is supposed to take care of that. Seems to me that you have two possible paths to take. One is to check the anode in six months or a year and see how it’s doing. Replace when six inches of the core wire is exposed. The other way is to install a powered anode, so the periodic checking is no longer needed.
As to sediment, I’d probably flush it at least every six months, to help keep sediment at bay. Flushing parts and anodes are sold on this site. Also, do check the relief valve and replace as needed. 😎
ps. Before doing anything, have a look into the combustion chamber and make sure there is no serious damage there.