Congratulations Finn....you just saved the Multiverse...and farm world Finn....not bad at all.
Edit:
We also have an idea of what Finn's max lifting weight is. He had trouble with the device Prismo gave him, which he stated felt like 50 bowling balls on his chest. Now a bowling ball's max weight is 16lbs (according to my research), so Finn starts to tap out around 800lbs...without his sword drawn (might be double that with his new blade). Now add in the fact that the device was unbalanced in design (plus Finn's lifting posture was frankly horrendous) and it's not outside the realm of possibility that Finn can lift 1,000lbs at his max, with his teen body. Since Finn is 14-15 years old right now I fully expect him to get stronger as he get's older....though by how much I am not sure.
edit:
Going by Marvel Comics Standards Finn is at Peak human range (2X own Body weight - 800lbs) to Superhuman range (800lbs - 2 tons)