If your outlet baffle was broken, then your system almost for certain has sludge transferred from the tank to the drainfield. This is the sludge inside the pipes. I do not know of any chemical that will dissolve this sludge. It is generally removed by "jetting". This needs to be done first before any treatment of the drainfield. If you have a header system, then you might need to expose the ends of each drainage pipe and clean it up back towards the header.

After the lines are cleaned, then the drainfield can be dewatered and Septic-Scrub(TM) drainfield flow restorer used. 

Your question regarding using a pump to push the water into the laterals probably would not do much good. A pressure system such as you describe is balanced so that the laterals and the exit holes are spaced so that the pressure drop is controlled and each lateral is fully utilized. Pressure system laterals are generally 2" pipe instead of 4". Pressure system are engineered to function fully. I have never run across a retrofit from a gravity to a pressure system without the entire system being rebuilt.

The best way to determine if the laterals are free of standing water is to drop a posthole into the drainfield and monitor the water level. If the field is dewatered, then when there is no standing water in the stone, then system is ready for a Septic-Scrub treatment. 

Even if you do not use Septic-Scrub, please consider putting a riser between the tank and the drainfield. I generally suggest bring a piece of 6" PVC pipe up the surface and capping. This allows you to monitor the water levels in the field and gives you a treatment port if you need to treat the sytem.

If you have any questions, you can drop me an e-mail with a time to call you and I will contact you.