you need to avoid repeating the position. triplechecking each cycle will be difficult especially once pawns start fillig up the board.
Theoretical Ceiling for FFA Score and FFA # moves

Dashes and Underscores, very true. The kings will have a limited amount of space and will have to eventually go behind enemy pawns. And behind the pawns are your rooks, bishops, and queens which have to be placed behind, say, knights in order to prevent checkmates on enemy kings.

Icystun it’s just a model with the assumption that triple checks happen every turn. It would be difficult to come up with an exact number. You might be asking where the 43 comes from to make 151083 that’s the remaining opponent’s pieces.
Disclaimer: I encourage people to play a fair game of FFA at all times. I do not encourage people to collude and prearranged team to make anything like this happen, but I'd like to share my analysis on the theoretical high score and highest number of moves in a FFA game. These are done in phases:
Phase 1: Opponents get their kings out, moving pawns up only one square each and get their kings out. Hero gets Queen out. Hero triple checks them 25 times in a row before Opponent one and opponent two alternate pushing their pawns one space. Assume a triple check every move cycle. Moves: 94x25=2350. Points for Hero: 94x25x15=35250
Phase 2: Opponent one and Opponent two both resign in a position where their kings are on the same diagonal or file. Hero triple checks kings every move for 50 move cycles. Then, hero and opponent three alternate pushing pawns every 50 moves. Moves: 94x25=4700. Points for hero: 94x50x15=70500.
Phase 3: Either a dead (grey) piece or a hero's or opponents piece, one at a time gets captured every 50 move cycles. Triple check every move. Moves: 60x50=3000. Points for hero: 60x50x15=45000.
Phase 4: Opponent one's king gets captured, and 50 double checks are made. Moves: 50. Points: 250.
Phase 5: Opponent two's king gets captured and checkmate is made on last player. M: 50 P: 40.
Grand total: Moves: 10150. Points: 151083.
More moves can be made if point strategy isn't made. If only one pawn is pushed at a time every 25 move cycles in the opening, then 94 becomes 96 in the two described phases (no triple checks can be assumed) and 150 moves are added for a grand total of 10300 moves.
tl;dr The highest possible score is 151083 and most number of moves is 10300.