Decidido por

Decidido por
 

seria decidio por=decidiria por
estaba caminando=yo caminaba

are these really correct?

It would be decided by = sería decidido por
(I) would decide for = decidiría por

Estaba caminando does not equal caminaba, even though the English translation is the same for both (I was walking). The first is a progressive tense. The second indicates an incomplete action or habitual action, or it sets the stage for something that occurred in the past.

I agree, Rusty, they are not the same. However, there's sth in the comparison with English that makes me feel uncomfortable...

Let's elaborate:

Estaba caminando cuando el policia le dió el alto

Caminaba por la carretera cuando...

Both tenses leave the action unfinished and set the stage for another action. Habitual actions in the past, well, a bit like English, they may need some explicit adverbial phrase, or even a periphrasis. Past habits are never build with a progressive form:

Yo caminaba todos los dias por la playa antes de comprar el pescado.

(More natural)

Yo solia caminar todos los dias....A menudo/todas las mañanas caminaba por la playa

In general, Spanish speakers may regard the distribution of simple and continuous as a stylistic variation.

Sorry if I don't sound very academic, I'm just talking as a user:hmm:

I agree. I have been trying to sway new students of Spanish away from overusing the Spanish progressive (continuous) tenses in this and other threads.
We frequently use the progressive tense in English. New students of Spanish tend to latch on to the 'cognate tense' and try to use it the same way, but they aren't always the same.