There is also no guarantee that either party will facilitate LN transfers in the futures and be willing to pay/accept what the other party deems to be a reasonable LN fee.

If Bob doesn't offer intermediary services or if he charges incompetitive fee for conducting payments, it's better to open a channel not with Bob, but with a competitive hub and route the payment to Bob through the hub. If Bob's channel capacity with the network isn't enough, he can open another channel with a hub.

then you could attempt to broadcast a settlement transaction that is not the most recent, that would result in you receiving more BTC than what you and the dealership have most recently agreed to -- in this situation, the dealership should normally be able recover then entire balance within the channel before you can spend the portion spent to you, however doing so would incur an additional tx fee that the dealership would need to bear in it's entirety in order to claim an amount that they are due anyway....and you are not risking very much/anything when you attempt to steal these funds (at most a nominal amount).