Your interpretation of 浴びせかける is essentially correct, though it should really be "was thrown upon me" since 私 is presumably the unstated subject of the passive construction. 浴びる and related constructions can refer to light in the same way as liquid, as you can see from the definitions given for the base word.
Your translation of the full sentence seems a little confused regarding how the elements of the sentence relate to one another, however. I would literally translate the sentence as something like:
"From beyond the darkness which precisely corresponded to the opposite lane to (that which I had been travelling along) so far, the dazzling beam of a lamp was cast upon me."
A few notes on how this differs from your translation:
- You seem to have interpreted the の of 闇の向こう as a descriptive/copula usage (equivalent to 闇である向こう), as if 闇 were being used as a の-adjective, but this is incorrect - 闇 is a simple noun "darkness" here, and the の construction is the basic Xの向こう meaning "(the place) beyond X".
- As such, there is no copula in the sentence to be modified by ちょうど; ちょうど modifies the verb あたる, meaning "precisely corresponds to".
- the これまでとは is directly modifying 対向線路, specifying that it is the lane in the "opposite direction as up until now". I'm not entirely sure what this refers to without context - in my translation, I've assumed it simply means the opposite direction to the one the speaker has been travelling along, but the construction seems perhaps a little overcomplex for this. It may be that it's referring to the lane being the opposite direction from, eg. some other lights that the speaker has seen coming previously.
- Your translation seems to be missing a translation for ライト (or conflating it with 光). This word refers not to the light itself, but to the artificial light source casting it (from the context, I would guess the headlamp of a vehicle.)
I hope this helps.