Just type "bump" or "ttt". Don't be a dick and post what you did post. Something else that would help is breaking up your post a little bit. That's alot of words shoved together. Each issue can have it's own paragraph/bullet line to make it alot easier to read(as seen in my reply below).
Problem 1: 'chatter'. I would say it's either valves or rockers or even it's just fuel injectors. I can hear my individually 'tick' when they inject the fuel. That's totally normal.
Problem 2: 'raising RPM w/ no throttle push'. IAC valve. It controls the idle and what actually keeps the rpms up on warm up. When they stick, it causes the engine rpm to stay at the same spot where you pushed in the clutch. Change it.
Problem 3: 'oil burning'. What exactly did you spend $2000 on??? If there's oil being burned, there wasn't a re-ring job when the pistons were put back in, and/or the cylinders wern't checked for roundness/squareness/bored. So...what exactly was done to the engine when it was 'rebuilt'?
Problem 4: '17mpg when it used to get 20'. Simple: Engine break-in. Engines take time to fully seat and make good numbers.
You're past the initial break-in period and shouln't be running such a thick oil in it. 10w30 or 5w30 is what you should be running. Right now you're running diesel oil. Also, when one issue is cured, it could bring out more issues you didn't know you had. Like the IAC sensor or other sensors on the engine. Are you throwing any codes? Was there headwork done when they did the engine(whatever they actually did)?? Deck the block, check heads for square? Went through and checked all the valves and replaced the guides? etc. What exactly was done to the engine?
'01 XLT disguised as a '03 Fx4 Level II.