We need pics. We are all pic whores!
As for the repairs, I will tell you, you have a lot more patience than others on the forum. As for the leaking ruby fluid, that would be power steering fluid since it uses standard ATF. But... Since you had the trans replaced; depending on where, a different fluid could have been used. OE BMW fluid is gold/amber in color.
As for the warning message, I have never encountered or read of the "Timing Guides Failure" in conjunction with the error message on the dash. Normally people just hear the failure. You also mentioned that the upper timing gaskets were replaced and would this be related to the timing guide failure... No. They are two separate components and I see it hard fit for the two to be related. Now if you said he replaced the timing chain and then you found out the guides failed, then I would question it.
Yes, the costs are staggering, but at the point you are at now, there is no return. Seems like the only other major thing to fail would be the Transfer case and the diffs. Sure the cost of the repairs will soon surpass the value of the vehicle but you need to ask yourself this. Lets say you can get $15k for the 4.6is, are you able to find another vehicle of the same caliber for that much money? If this were my situation, I would run it until the door panels came off or until the window regulator broke again because you shut the door with the windows down. Either or.
Have fun and post some pics!