What type of keyboard is actually on your computer? I think the fact that you are using only the Japanese input for both Japanese and non Japanese (I assume both Spanish and English) is what is messing you up. When I changed my settings to exactly what you have setup I also could not type the opening quote character like I normally would, so its definitely your settings.
Here are some suggestions to try:
First, use the appropriate input method for the language you are typing in. Your computer actually uses separate dictionaries for the language of the keyboard you are using. This is why you see multiple keyboard layouts for the same language even though that might not be the default for that country. Using romaji to type in non-Japanese languages messes with what your computer assumes you’re going to be doing. You will still be able to use your alt + up and alt + down shortcuts to switch between languages exactly the same way as you can now. (assuming you set them as “Select the previous input source” and “Select next source in Input menu” in your keyboard shortcuts)
Turn off romaji input. The only option I have selected in my Japanese keyboard is hiragana. Chances are if you want to type in romaji, you aren’t writing just a single word in Japanese, so it’s better to use a different input. Use the Spanish keyboard for writing in Spanish, the flavor of English you prefer for writing in English. You’ll get many benefits unrelated to they keyboard layout.
For “romaji layout”, choose whatever matches the physical keyboard on your computer to make things simple.
To type an opening quote, press just the
[ key, without alt/option. I think this is what is throwing you off. I see that on the Spanish ISO, you can’t actually type a
[ without using option, but it might be bypassing the IME and typing just that character. Are you using alt +
[ because it shows up as a backtick ` otherwise? That’s what happened to me when I switched to Spanish - ISO, like you have, for my romaji input. If that’s the case you’ll probably need a different binding for the opening square bracket key.
Finally, have you tried resetting the custom dictionary for your keyboard? At the bottom of the Input Sources menu the option is “Conversion Learning: Reset…” try that out. It should reset any learning your keyboard has done, and put it back to the default dictionary. I don’t know if typing in Romaji input mode in other languages can influence this dictionary, but it might happen.