¿Es correcto decir 'should to'?

nope. los verbos modales nunca van con "to". Siempre es el modal + verbo. I should go now. (should, must, could, would...)

Should + infinitivo No lleva to

Never. Should is a modal verb and modals verbs are followed by a bare infinitive (without to). Nevertheless, you can use the modal verb 'have to'

should/must + infinitive without to

No, it's not correct. The preposition TO is never used after a modal verb, except with HAVE TO or OUGHT TO

Structure: subject+should/must+infinitivo. Cheers

It would be better to say "You should go to" or "You must do this" but should and must are not followed by too because they are modal verbs, which are different from normal verbs. I hope that this helps clarify your doubts Veldina.

Si quieres usar un modal de recomendación/opinión como "should", debes tener en cuenta que va seguido del verbo en forma base . Sin embargo, tiene un equivalente, "ought to", que rige "to". Ejemplos: Deberías ir al médico - You should go to the doctor/ You ought to go to the doctor.