Answer
As salamu `alaykum,
It would seem that there is a big gap between your parents, in-laws and yourself in terms of lifestyle. Obviously, both your parents and your in-laws come from a lifestyle that was very much based on the demands of farming and providing for a family. I assume (from experience) that it is also the case, that your parents generation come from a less individualistic generation; where common values, and privacy are less common and accountability to each other and for each other is much more important. This I must say is a favorable way to live as long as the Islamic values are not undermined by cultural values, especially the kind of values that inculcate little injustices into daily life.
Being brought up in a totally different environment to your parents can increase the gap greatly between ones self and ones parents. At the same time, cultural understandings of certain Islamic practices can be corrected if as the child, one takes a great interest in establishing what is correct within Islam. Done with compassion and understanding, your parents might not change (due to age), but they might begin to accept.
{Abu Huraira reported: The Messenger of Allah (may peace be upon him) entered the mosque and a person also entered therein and offered prayer, and then came and paid salutation to the Messenger of Allah (may peace be upon him). The Messenger of Allah (may peace be upon him) returned his salutation and said: Go back and pray, for you have not offered the prayer. He again prayed as he had prayed before, and came to the Apostle of Allah (may peace be upon. him) and saluted him. The Messenger of Allah (may peace be upon him) returned the salutation and said: Go back and say prayer, for you have not offered the prayer. This (act of repeating the prayer) was done three times. Upon this the person said: By Him Who hast sent you with Truth, whatever better I can do than this, please teach me. He (the Holy Prophet) said: When you get up to pray, recite takbir, and then recite whatever you conveniently can from the Qur’an, then bow down and remain quietly in that position, then raise your- self and stand erect; then prostrate yourself and remain quietly in that attitude; then raise yourself and sit quietly; and do that throughout all your prayers}.
Here we have an example of going into ruku` (bowing) and remaining quietly in that position, of going into sujud (prostration) and remaining quietly in that position. The person spoken of in the ahadith had to repeat his prayers three times until he obtained the conditions necessary for prayer. Can these conditions be met by praying quickly?
The process of digestion begins in the mouth, not in the stomach. How much we chew what we eat eases the burden on the digestive system and reduces the formation of many illnesses from bad digestion. The all important salivary glands also play a role in detoxifying the food we eat.
So, it looks like, on the count of your eating habits and your praying habits you are not doing too badly. The next important person who should know this besides you is your husband, after all, it is through him that both sets of parents are weakening your marriage.
Once you can be confident not just about the rightness of what you are doing, but that you have a right as a married couple to decide between the both of you what is beneficial to your marriage and your family, then the nagging parents will run out of steam, at least on this matter. They only have this destructive control over your marriage, because you allow them to. It is possible to maintain healthy relationships with your parents, once you make the limits clear (through your actions) and to be a good mother and a wife.