How do I plot linear regression results if input and target have different sizes?
You can plot your residuals. I am sorry I can't write it in Python but in R you would do it like this:

plot(my.model$residuals)


This will give you a scatterplot that you WANT to look like a null plot. Any curve or pattern in the points means that your model is not a good fit.

If you are interested in assessing each variable's prediction power I recommend (because you only have six) doing 1 regression model on each variable by itself and then plotting the residuals of those models, again looking for a null plot. You can also look at the correlation of each predictor variable vs your response variable. Those with higher correlation will be better predictors.