As per the fatwa of all grand jurists, all non-believers including Hindus are ritually impure. Supreme Leader, grand Ayatollah Khamenei and a few other prominent jurists are of the view that non-Muslims excluding the People of the Book (Christian, Jews, etc.) are impure. Likewise, the animals (sheep, cows, chickens, camels etc.) slaughtered by non-Muslims are impure and haram to eat. Therefore the foodstuffs which are prepared with the meat of an animal which has been slaughtered by them are impure. The position is the same with the food which has been prepared manually and which has certainly come into contact with the moisture of their body. As for the food which does not contain meat or contains meat of halal fish, it is permissible to eat provided that it is prepared either with machine or it has not come into contact with their hands and moisture of their body.
According to the verdicts of Shia jurists, it is not permissible to eat from marine animals anything except fish that has scale. Also, sausage and soya are halal, if they do not contain intoxicating and impure ingredients or haram meat. That is only when they have not come into contact with the body of an unbeliever (kafir) or with the moisture from his body.
The detailed answers to the foregoing questions are as under:
Based on the fatwa (verdict) of all religious authorities, a Kafir (unbeliever) is ritually impure and it is necessary to avoid coming into contact with the moisture from or on his body.  Since Hindus are polytheists  and they are considered to be idolaters in a way, they are impure. Therefore, if one is certain that a specific thing or a utensil has reached the moisture from a Hindu’s body and the moisture has transferred it, it has become impure and you will need to purify it by rinsing it. 
Although your parents are non-Muslims and you are Muslim, you should respect them as far as you can.
According to the verdicts of all Shia jurists, that which can be derived from the narrations is that it is not permissible to eat from marine animals anything except fish that has scale.  As for lobsters, sharks and octopuses, they do not have scales and they are not even considered to be from the category of fishes. Therefore, it is not permissible to eat their meat  and they do not become halal with the certification of a Sunni association.
If the people working in the kitchen are people of the Book (i.e. Christians and Jews), according to the verdict of those jurists who consider the people of the Book to be ritually pure, you can eat only the halal food of the restaurant. However, according to those jurists who consider the people of the Book as impure, the people of the Book as well as the all types of unbelievers are impure and in case one is certain that they have touched the food with a wet body and wetness has transferred from their body, there is problem in eating the food. 
Therefore, according to all the grand jurists, those who are working in the kitchen and are not Muslims or people of the Book (Ahl-e Kitab) are impure and if the food or anything which is in the kitchen comes into contact with moisture from their hands or body, it will be rendered impure and it will not become clean by a certificate.
Chinese and Indian sausage, soya, chips and snack would be halal in the following circumstances:
1. No intoxicating ingredients should have been used in them.
2. Meat, their extracts and any impure and haram object should not have been used in them.
3. It should not come into contact with the body or the moisture from the bodies of nonbelievers.
Hence, if one of the above conditions is not met, eating the food in the question will be haram and it will not become halal by way of a certificate or label.
For further information about haram animals vide: answer 2166 (site: 2290) (Animals whose meat is haram).
 - Islamic Laws (with annotations by Imam Khomeini), vol.1, pg.1, pg.76, issue no.106. Publisher: Islamic Publication Institute affiliated with Society of Teachers, 1424 A.H.
 - Serat al-Nejat by Ayatollah al-Shaikh al-Tabrizi, vol.6, pg. 373.
 - Excerpted from answer No.1082 (site: 1173)
 - Islamic Laws (with annotations by Imam Khomeini), vol.2, p.595.