But God has never changed and what He ultimately expects of people has never changed. Caleb and Joshua did not make it into Promised Land because they were able to and did precisely obey the letter of the written laws God gave to Moses... Rather...
"But my servant Caleb, because he had another spirit with him, and hath followed me fully, him will I bring into the land whereinto he went; and his seed shall possess it." Num 14:24
The difference now for us is not that God has changed His expectations, but that he has offered a Way to Him without a special man of flesh, a priest [Aaron and sons] always ready to make the connection for us. Now we may be the priest and the rules/laws to obey are to be written in our hearts. The interpretation in the OT was done via another man, found in a human priest or prophet, but now we may be the priest or prophet ourselves with the Interpreter being the Holy Spirit in us. Caleb and Joshua were not legal experts empowered to obey God precisely by their ability to interpret the laws given to Moses but their hearts were pointed in the right direction by that same Holy Spirit... because they loved God. Do we?
If we do, then like Caleb and Joshua we will be allowed to enter into a special place with God... If we love God will we not be seeking always to go His exactly prescribed Way rather the a way which gives of the best to two worlds? This last is double minded and lukewarm and ultimately will cause us lose all that we have been given by God. God's exact and prescribed Way cannot be found by Bible study alone! Ask the scribes and Pharisees who surely knew the scriptures without knowing God!
You speak of the letter of the law, even though you designate it NT law as opposed to an OT law.
"Jesus Christ the same yesterday and to day, and for ever." Heb 13:8
Do we love His promises and blessings more than we love Him? We need to understand the difference between loving the rewards and loving Him?
Looking for letter of the law loopholes according to what is written in the NT is trying to do with the NT what was impossible and unacceptable for men in the OT and is unacceptable now:
"Now therefore why tempt ye God, to put a yoke upon the neck of the disciples, which neither our fathers nor we were able to bear?" Acts 15:10