Perhaps this will give you some idea how to approach this problem.
A number of the assignments in your large file are not used. I hope this doesn't mean that the moment you get an answer that you will say you actually wanted something different.
You said that exp1 is the focus of your problem. exp1 is a simple numerator/denominator. I extract each of those and reorganize their form. This
Collect[Numerator[exp1], rr]/Collect[Denominator[exp1], rr]
very quickly returns a result where I then manually replace large expressions with corresponding simple variable names n6, n8, n9, n11, n12, n14, d6 and d12 just to be able to show and explain the structure of your problem in a compact form.
(-rr^6 n6-rr^8 n8-rr^9 n9-rr^11 n11-rr^12 n12-rr^14 n14)/(rr^6 d6+rr^12 d12)
Note that denominator is the only place in exp1 where rr appears in any denominator.
For each of the terms in the numerator that have rr to a greater power than 6, and assuming there isn't catastrophic cancellation, the numerator will go to zero faster than the denominator. That only leaves the
rr^6 to consider.
To look at this behaves as rr tends to zero I'll take a
Limit using my substituted variable names instead of the original large expressions.
Limit[(-rr^6 n6-rr^8 n8-rr^9 n9-rr^11 n11-rr^12 n12-rr^14 n14)/(rr^6 d6+rr^12 d12),rr->0]
which very quickly returns
If it helps, an alternate way of writing that fraction is
(-n6 - rr^2 n8 - rr^3 n9 - rr^5 n11 - rr^6 n12 - rr^8 n14)/(d6 + rr^6 d12)
You can automate putting exp1 into this form using
newexp1 = Collect[Numerator[exp1], rr]/Collect[Denominator[exp1], rr] /. rr^n_ :> rr^(n-6)
I believe this result might imply that if your large expression were suitably arranged that terms in your your fraction do not blow up as rr goes to zero, but instead go to zero because the powers of rr in the numerator are greater than the powers in the denominator thus leaving that relatively simple fraction.
You haven't said what it is that you want to do after you were able to extract the terms which blow up when you replace rr with zero, but perhaps this can give you some idea that you might be able to use.
Hopefully at least this might let you see that your problem might be considerably simpler than it originally seemed to be.
Please check all this very carefully for correctness before you depend on it.