Which Item should be priority assuming I can't afford all at the same time?

Ouch. I would go 3,1,2.. but you may not have that option. To get this car running right, you may be forced to do all of the first 3. 4 and 5 can wait a little longer - but if you are already 20k over your 40k recommended tune-up, you dont want to push that one. That is possibly the reason you are having the issues with 1,2, and 3. good luck!

I would do the miss fires first because if you dont you may kill the cat which would add about 1000 to your repairs. Roy

Dear Rookie If your vehicle information posted is correct the issues you have listed are of concern but your main concern should be the fact that your timing belt is 10 years old and if it breaks the results are catastrophic!!The rule in the real world of interference engines such as the one in your Passat is to never go more than 5 years or 60k miles. Granted the problems you have listed are real and should be repaired. If you are original owner of this vehicle,VW should have sent you a notice of Ign coil replacement under a recall bulletin.When having this recall done the dealer would be able to install your spark plugs for a nominal fee because they are servicing your secondary ignition problems.Again the timing belt issue is the greatest concern you should have.Also if coolant reservoir is not cracked just clean it. A proper t-belt service includes w/pump replacement with new coolant.