Hey, there. I'm a novice here. I let myselt to give you a piece of advice:

I really have no idea why not to use MAY/MIGHT.
Treat the CAN as TO BE ABLE TO (Иметь физическую возможность)
and the MAY as TO HAVE A PERMISSION FOR (Иметь разрешение)

Can I go there? = Я могу (физически) пойти туда?
and
May I go there? = Разрешено ли мне ...?

Use could/should/might as a "сослагательное наклонение" - БЫ/ЛИ-versions, like less agressive variant of saying something:
Can you do it? = Вы можете сделать это?
Could you do it? = Не могли бы Вы сделать это?

You shall avoid obstacles. = Вы должны избегать препятствий (на дороге).
You should avoid obstacles. = Не могли бы Вы избегать... (более мягкий вариант).

You may do it . = Вам разрешено сделать это.
You might do it. = Вы могли бы сделать это. (Like: You are permitted to do it....)

If I eat these fifteen sandwiches, I might be thought as a glutton (literally - "мог бы быть подуман ....")
sounds like: people [have right to] (may) think of me as a glutton.