Comm Prop - Tenant Lease contract RENEWAL question

[socalrws]

Location is in SoCal - Riverside Co.
Tenant is a anchor - a national Paint supplier in 10K sqft storefront retail tilt-up, since 1990
3 units in 20K sq ft bldg. 2 are rented. one is empty for last 2 yrs. 
Market has gone from $0.85 -> 0.60/sqft

October their 5yr lease is expiring and our manager says there are rumors of them wanting to MOVE OUT! In the past years we have gave them a reduction in rent due to losses in their market and not wanting them to move, it was at their request.  Our manager says he would like to negotiate the lease renewal and if successful wants 3% commission for the life of the contract.  He has no guarantee he will win a contract.  With past in-house managers it was a fixed fee. 

Does the offer(3%) and rumor passing of manager sound suspect?  What else should we be aware of?
(It's my moms property, she's 85)

Our thinking is to write the corporation lease person with an offer to match any competitive bid and they will not have to move.  Also mention the property improvements in the past five years and the cost to us.  There are some major ones, like removal of 60ft tall palm trees surrounding and obscuring the bldg, a dozen palms were damaging the roof;  Roof was re-roofed and has 10 yr warranty (expansible to 18); concrete driveways/parking scheduled for re-paving to meet safety inspections codes. New landscaper hired to improve appearances of lawn and garden areas.

Any general advise on lease renewals?