It seems there might have been some confusion somewhere. LNF is not a special code. It's simply Marriott's guarantee that they'll give you the best rate (i.e. their Look No Further Guarantee). If you can't find a better rate elsewhere, you don't need to worry about LNF. If you're happy with the rate you have and don't want to keep searching, you don't need to worry about LNF.

Because LNF rates are booked through Marriott, there's no reason they shouldn't qualify for points or night credit. Similarly, if you book through Marriott.com with a rate code, you should receive the points and night credit.

If you want help searching for LNF possibilities, try posting to this thread. If there's something better out there, hopefully someone will be able to help you.

Again, if you book directly through Marriott, you shouldn't be worrying about whether you'll get points. And again, if you're happy with your rate and don't feel like playing the LNF game, just keep your reservation as-is and be enjoy your travels.