Hi and welcome MrHHome!
As a Christian non-jw who has been with and around JWs for 2 years now I can tell you how it has worked with me. This is going to sound insulting to some, so let me reiterate... this is MY experience.
JW: 1 Cor. 7:39 says we (JWs) MUST only marry in the Lord.
Me: Hm... contextually, I'm thinking Paul was considering the three groups in existence at that time - Jews, Non-Jews, and a new group of a mix of the two that believed in Christ. I see nothing here about marrying only JWs. Let's read the chapter together...
(we read)
Me: Hm... looking at verse 25, it appears that Paul is acknowledging that this is his opinion...
JW: It doesn't matter, verse 39 is scriptural and all scriptures are inspired by God and useful...
Me: uh.. are you saying that verse 25 isn't scripture?
(this question is followed by a meltdown in the conversation)
MY experience (with about 7 different JWs) is that they have phenomenal comprehension skills when it comes to reading WT literature, however, know that they are not going to interpret scriptures in the way that we've always known and more often than not, they'll read them but the mental block is too strong. Many times I was dead sure they'd HAVE to acknowledge that what they were saying and what the Bible said were not the same only to look at them and realize a creepy "doe in the headlight with gentle smile" stare after the reading. As you begin to discuss the passage, you realize that they read but didn't contextually consider the verses.
Just this past weekend, I had a woman emphatically state that ALL of the 144,000 were JWs. I responded, "Hm... I REALLY could have sworn the 144,000 were Jewish males who were virgins. I then turned to Rev 7 & 14 (to check myself with her looking on) and read the passages with the two ladies... the response? A short silence followed by, "Nope... see... what you don't realize is that some of the 144,000 are married."
Reading Revelation 19:1 resulted in two different responses (two different JWs)
REJOICING IN HEAVEN (caption preceeding verse in ESV)
"After this I heard what seemed to be the loud voice of a great multitude in heaven, crying out,..."
For us non-jws, "okay... great crowd in heaven cried out... got it."
JW Response #1: "That verse says he heard 'what seemed' to be a loud voice of a great multitude in heaven! That doesn't mean it was in heaven! Furthermore, it is dishonest of the ESV to put that caption on there when that's NOT what the Biiiible says! (they drag out the "I" in Bible when they are making the point that only THEY are following the Bible)
JW Response #2 who is sitting with another woman: "See, what you gotta understand is that there are lots of angels in heaven and THAT'S the crowd this verse is talking about but THAT'S not the crowd we're going to be in. ...unless you're thinking you're going to be an angel or something! (said with a sarcastic chuckle) See you're confused... you're so confused."
Be ready to practice a LOT of patience.