1) DoS attacks on the Lightning Network appear to be quite successful so far. What can you do about it? Also does it cost the attacker money (as in blockchain spam)? ( https://twitter.com/alexbosworth/status/978069194385252352?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E978069194385252352&ref_url=https%3A%2F%2Fcoincierge.de%2F2018%2Fbitcoin-lightning-netzwerk-fehler-verlust-von-bitcoins%2F )

I hope every attack makes the network stronger as intended but I'm glad to see the Layer 2 payoff that the btc blockchain isn't involved too much in this very new experimental phase.

2) And do 51% attacks get more profitable with Lightning attached to it?

I refer to https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-March/001080.html Rene Pickhardt wrote but  maybe just don't understand how it works?

Also I'm not a game theorist so I dont know the chances of honest work vs 51% attack regarding a somehow unknown amount of money.