Encapsulated Crawlspace Odor and Vent Fan Advice

We recently purchased a brick rancher that had the crawlspace encapsulated two years ago. All crawlspace vents are sealed off. There is a dedicated Santa Fe branded dehumidifier to a sump/pumpout. RL is 35 to 40% in the crawlspace. There is also a small hvac supply duct to the crawlspace and one of the house registers was deleted to allow makeup air. We are getting an ammonia-like smell inside, especially when running bathroom exhaust fans. Its not so bad during summer with the AC running a lot, but with the cooler weather the smell is pretty bad.

Im reading this occasionally happens and is due to soil decomposition gasses. It seems that an exhaust fan in the conditioned crawlspace is recommended at 1 cfm per 50 sq.ft of crawlspace. This overcomes the slight positive pressure in the crawlspace due to supply duct and also keeps the odors from building up and entering the living space. For our 1500 sq.ft crawlspace, this would be 30cfm.

Any recommendations on a fan with this low of flow? Any other ways to mitigate this smell? I am tempted to put a Panasonic bathroom exhaust fan set to lowest 50cfm setting and duct it out of a hole in one of the existing vent grates. They are rated for continuous use. I have also considered eliminating the supply of conditioned air and return grate and relying only on the dehumidifier and small exhaust fan. The company who encapsulated is non-helpful and several calls to other companies seemed to dismiss smells or wanted to rip everything out and install a Radon mitigation system under the liner - which sounds great if it had been done from the start, but majorly expensive now.