How do we comply with FinCEN and Title 31 laws/ regulations?

I would like to begin trading on LocalBitcoins, LocalEthereum and similar fiat-to-crypto peer-to-peer exchanges. I am trying to find all the rules I have to follow to do this legally but from the articles I've read about people being arrested for trading on LBC, it doesn't appear to be black and white. While some of these guys were clearly breaking the law, there are some instances where a trader is arrested for "running an unlicensed money transmission business" with not much detail on exactly why or what specifically what rules were broken.

Here are just a few:

• Man and father trading on LocalBitcoins sentenced to 9 and 4 years in prison respectively for running an unlicensed money transmission business

• Michigan LocalBitcoins trader pleads guilty to running an unlicensed money services business (sold $1900 worth of BTC to undercover agents)

• Missouri LocalBitcoins trader pleads guilty to running an unlicensed money transmission business (sold $30,000 worth of BTC to undercover agents)

• New York man pleads guilty to unlawful money transmission (sold $13,000 worth of BTC to undercovers then lied to the feds about it)

• Two LocalBitcoins traders from Florida charged with money laundering and running an unlicensed money transmission business (tried to sell $30,000 in BTC to undercovers. This one says they're being charged with state-level crimes, not federal)

• Las Vegas LocalBitcoins trader arrested for money laundering and running an unlicensed money transmitting business (sold $9000 worth of BTC for $14500 to undercovers that told him the cash came from selling hash oil)

I'm sure there are plenty more.

So far, I've summed the morals of these stories up to the following:

• Don't trade more than $10,000 at a time, though it is probably wise to stay much lower than that.
• Don't trade with anyone suspected of engaging in illegal activity using the BTC/ whatever that you're trading to them.
• Consider registering as an MSB with FinCEN (not sure what other hoops there will be to jump through with this).
• Don't violate state laws.

Currently I'm attempting to read through the FinCEN website and Title 31 itself but they're not exactly written for laymen. Does anyone have any insight there can share on this topic? Any help or guidance at all is appreciated.