If I can clarify some of this... I'm sorry you lost your stuff because someone stole it, however the server forums have several posts urging people to protect your valuables. We are an open server, we are providing a means to protect your gear...if you chose not to claim your chunk, you can hardly blame others. I recall seeing you online several days for several hours, so there was ample opportunity to claim your chunk. The cost is at most 5 diamonds and should not take hours and hours to find. If you had time to accumulate enough stuff to be miffed about losing it, I would think diamonds would have been high on the list to go hunting for before anything else?
The donation packages give minor perks. Like a few dynamos, some nitor, some hobbyist and redstone engines. Access to some items that if everybody could craft them would cause server issues (Mystcraft, for example). Extra /homes. Yes, they give diamonds, but nothing extravagant. A diamond enchanted tool set. The highest level donator perks was just more of the same, with a diamond pick that you can't even repair, so it's only one-use. The highest tier item you were given was a compact windmill and an MFSU. After the update, those higher tier items were removed and not part of the donator kits. Donators also get the perk of being ABLE to craft some items that are otherwise banned, but by the time you have the resources to do so, their benefit is somewhat mitigated. You are not given those items, you have to obtain them on your own. You are also ABLE to claim more town chunks to protect your builds, but you still have to pay your own diamonds to do so. So I disagree entirely with the assertion that the server is "pay to win". I am a highest tier donator and aside from the diamond tools, I have not used any of the items I was given since the update until I at least crafted one of them on my own. There is no intrinsic advantage over other players for donating, other than feeling good about it and getting a little bit of a head start out the door.
The lag I'm not qualified to address, however we also just had a major update to our pack after adding two or three major mods, and it is still being shaken out.