When conversations like this come up, I think it is a good practice to have a Catechism of the Catholic Church handy (or similar resource material that conveys the official teachings of the Catholic Church). That way you can properly represent what the Church teaches so that your in-laws can understand what Catholics and Pentecostals have in common, and where there are differences in doctrinal understanding.
If your in-laws are trying to pressure you into leaving the Catholic Church because they believe some of the teachings of Catholicism are wrong, then ask them what authority are they appealing to in order to make such a judgement. After all, this is not a simple matter of them reading and reflecting upon the Bible in order to live their lives as better Christians, but rather it is about them taking this further by setting up their personal interpretation of Scripture (and/or that of their pastor) as the standard that all Christians are to follow (including you). In other words, they seem to be insisting that you need to do things their way in order to be saved. So with what authority do they insist that their interpretation of the Bible and Christian living is correct and the teachings of the Catholic Catechism are wrong? If they say, “The authority we appeal to is the Bible” then point out that the Catholics also believe that God’s revelation is found in Scripture (as well as Sacred Tradition) but the discussion at hand is not simply about what the Bible states, but rather about how it is to be interpreted. For example, among the Pentecostals there are those who believe in the Doctrine of the Holy Trinity (one God in three persons) and those who do not (i.e., the Oneness Pentecostals, who believe in one God as only one person). So even among Pentecostals there are differences in how the Bible is interpreted. Who is right and who is wrong?
As Catholics, we believe that the Magisterium (i.e., the teaching office of the pope and the bishops in union with him) has a guaranteed guidance of the Holy Spirit to officially define Christian doctrine free from error. So that is the authority that we appeal to in defense of the official teachings of the Catholic Church in matters pertaining to faith, morals and salvation. If your in-laws claim that no one on earth has this authority then you can point out that even though they say this, they are acting as if they think that they personally have such an authority. Keep in mind that if they convey an attitude such as, “My interpretation of the Bible is the correct one and the Catholic interpretation is wrong, so you’d better listen to me in order to be saved,” then they are, in essence, acting as their own pope and expecting you to go along with it. If this is, indeed, their attitude (even if they don’t admit it) then ask them what makes them the pope and not Pope Francis? Hopefully this will help them realize that despite how sincere their beliefs are, they have no guarantee that their personal interpretation of biblical teachings is without error and therefore they shouldn’t be trying to force them upon you as if your salvation depended on it.
For more on this, please read: What’s Your Authority.
In terms of the concerns you have over immoral things that sometimes pop up in the Catholic Church, then please know that I share your concerns. But every Christian denomination, as well as every religion, has them. The Church on earth is not so much a museum of the righteous as it is a hospital for the sick, and in this case the sickness is sin. Just as sick people go to the hospital to be treated, sinners go to the Church to be treated, so we shouldn’t be surprised to find sinners in the pews. God instituted the Church to be a channel of saving grace in the world, so the members of the Church are, by definition, in need of such grace. Some people embrace this grace (and live it) better than others. So while we are the Church of such exemplary people as St. Francis of Assisi, St. Therese of Lisieux, St. Augustine and Blessed Theresa of Calcutta (a.k.a., Mother Theresa), we are also a Church of people who have become hardened by sin and act badly, and even horribly. We are all in this together, and need to be there to help one another, knowing that a Church full of perfect members does, indeed, exist, but only in heaven. But the Church on earth helps us get there.
In terms of some of the other things you mentioned, the following material may be helpful:
Not By Scripture Alone
Scripture and Tradition
Faith and Works
Does the Church Teach that Works Can Obtain Salvation?
Speaking in Tongues
Concerning the passage from Deuteronomy mentioned, it may be referring to 22:5 which states, “A woman shall not be clothed with man’s apparel, neither shall a man use woman’s apparel: for he that doth these things is abominable before God.” But Scripture scholars are not sure what the context of this teaching was, and therefore uncertain of its application. Consider, for example, this commentary on the verse: Haddock’s Catholic Bible: Deuteronomy 22.
Later Edit: I misread imeldareye8’s comment about “their church” (i.e., the in-laws’) as being “the church” (i.e., Catholic). I apologize for any confusion my response caused. But because it was a side comment, I think the main question has been sufficiently answered.