Am almost done with A levels and am planning to do languages at Uni.
I only did french GCSE, and am only doing French as a language at A level, though am planning to pick up Arabic at uni.
My other 2 subjects are really random - Geography and Media. Although there have certainly been some low points with them during the last 2 years, I don't regret either of them as it has given me a much more varied education than had I confined myself to languages and closely associated subjects. This has also in no way disadvantaged me in applying to unis. So I cannot stress enough how important it is to pick subjects you enjoy!
The advantage of German over French is that German is (obviously) a germanic language, so a different family to French and Spanish, which are romance languages (Latin based). French could easily be seen as a cross between English and German.
It might be worth considering if there's anything you want to specialise in at a later date when picking between languages - French is far more suited to global history and politics than German which is likely to have a european focus.
I'm sure you don't need me to tell you this but starting from scratch will be a lot of work (but HUGELY rewarding) so I would quite strongly advise against taking 4 A levels in that scenario - though that is a decision for you and you alone to make based on how you perceive your work ethic.
Its great that you are passionate about english lit! As I'm sure you know the A levels have essay papers on film and literature - sounds daunting at first but its completely manageable. Although you are likely to be able to draw links with any subjects you choose (maybe with the exception of maths!). As an example I used a fact from my french exam in my geography exam the other day, and then a geography fact in my media exam. You don't necessarily need to go down the rabbit hole of tying all your subjects together in the hope they'll be complimentary!
I hope this was some (if any) use!