I have made 100's  of backing track I use live over the years ( 340?) 
In the past you rolled your own or paid for a tracvk
Now there is almost every top 40 song and most are free. People like me share our files.
SO first google for a MIDI file.
 
What your trying to do is not hard if the original material is a steady tempo.
It becomes more work if the song is a loose goose. 
Here's my method that will work with 80% of commercial top 40, modern country music. 
Plunk the audio track in DAW
Get as close as you can in tempo
Line up the downbeat of the first measure. 
Now mess with the fine tempo settings until the song still lines up with the grid at the end. 
If the song is a brick wall wave form that you cannot see the transients, make a midi transient track. 
Play your own click track along with the song.. in the end your going to re build a drum set anyways so use this and then quantize it. 
 

If I understand the OP's purpose at all, creating a tempo map is useless. He wants to create a backing track, presumably without wavering tempo. He just wants to use the original as a reference and is trying to line it up beat for beat.

I think he has been trying the right thing but perhaps some AudioSnap markers need to be adjusted.

Here is how I do it when attempting to do a cover that stays true to the structure and "tempo".
 
1. determine the average tempo, set it in SONAR
2. line up the first (in time) beat to a measure
3. turn off snap settings
4. cut up the beginning measures until you're out of time (typically 1 -3 measures but can be more depending on how tight the original recording was)
5. turn snap on (measure)
6. move the remaining song clip right at least one full measure
7. stretch/shrink the left clip to the nearest measure, bounce that to clip, lock it, this is no longer an addressable clip
8. slide the right clip (remainder of the song) left to align to the next measure after the locked clip
9. repeat steps 3 - 8 until the song is done
10. optionally  unlock all clips, select all and bounce to clip
 
It's time consuming but hey, it works. And now the "guide" in symmetrical in tempo thru the whole song*
 
 
*unless there are intentional speed ups and ****s in the song in which case you may need to make adjustments for that.
 
11. (it can always go to 11, huh?) Want to give the guide some energy? Do the process to the now full clip but this time in verse/chorus/solo/bridge/outro sections and speed up the choruses (or solos or bridge etc.) by 2-3bpm (if the song warrants it).

It seems to me, that the OP wants to keep the variations of tempo in the original. At the same time he wants to have Sonar's metronome be in sync.
If that is the case, then he should use shift-M technique to mark the beginning of each measure.
(or as often as needed to keep metronome in sync)
You can now play along with the original and MIDI will be in sync with measures/beats.
I use this often to lay down backing tracks for covers, it works great.