Where do you get these 99% stake stuff?
PoS coins use 10% of stake and dropping as economic activity goes up. Let alone that their profits are tiny to justify such big stake in minting (Just early adopters minting to support their system). If a real economy exists many will put their coins in more productive uses than minting and will not even care.
Again, this doesn't apply to Nxt because in Nxt minting with coins does not preclude them being available for other uses.
Why do you assume all these nodes will be online at the time of the attack?
People who don't want to be online 24/7 can lease to those that do. So a high proportion of coins should be online at any given time. (It's not like that now, partly because leased forging is new, and partly because I think some whales are keeping out of it to let other people gain forging revenue.)
Why do you assume that lending will be something everybody will do?
If you have sufficient coins that leasing pays for itself, it's the rational thing to do, with no downsides, so most people will do it. (Except the ones that have enough to justify running their own node.)
Why do you assume that it will not backfire giving one person extreme stake history who might not care about the coin at the present?
It's something we need to be vigilant about, in the same way the Bitcoin community needs to be vigilant about mining pools becoming too powerful. However, because Nxt forging doesn't have the same economies of scale as Bitcoin mining, there is less pressure towards centralisation.
Why do you say lend your coins to a person you can trust if you want to build a trustless system?
Because trusting a forging pool is no worse than trusting a mining pool (except you have a choice about which pool you trust, in Nxt.)
Why do you assume that the rest honest stakers (those not having their coins reversed) will not mint both chains?
They can only mint blocks when the algorithm picks them as the current forger. Minting blocks when you aren't current is pointless.
All PoS coins are very centralized in their stake distribution and dont forget that when you say they are decentralized.
Initial distribution is orthogonal to PoS. It's a problem for Nxt, partly because it's so new. It improves over time.
Total Forgers Revenue: 5500 NXT
So in a perfect liquid market of stake, I would want to wait about a day before accepting 350 mBTC worth of NXT.
I don't understand why you think there is a connection between mining revenue per block and the number of blocks to wait before considering they are confirmed.