The origins of the weird scoring terminology in tennis

Listening to a tennis umpire, or even the TV commentary, can be a bit of a bewildering experience until you get used to it. Even once used to it, it can be a bit puzzling until you know a little of the history of scoring in tennis. But even then much of it remains unexplained and mysterious.
Fifteen-love. Fifteen-all. Fifteen-thirty. Fifteen-forty. Deuce. It doesn't seem to make much sense. It's tempting to assume that fifteen, thirty, and forty (as shorthand for forty-five - there are mentions from the fifteenth century of forty-five, not forty, in tennis scoring) are based on the quarter hours on a clock, with a game marking a complete hour on a clock face. But minutes on a clock were not used until the late 16th century, and did not become common on clocks until substantially later than that, so that theory does not hold water.
Tennis developed from the French game jeu de paume, played with the palm of the hand rather than a racquet, and dating back to the thirteenth century, before morphing into real (royal) tennis and, ultimately, lawn tennis. In jeu de paume, a player winning a point moved forward fifteen metres for the next point, and then again for the next, and then ten metres for the final point of the game, providing a possible better explanation of the fifteen, thirty, forty progression. But even this is disputed.
As for the used of "love" to mean zero, a common supposition is that it is from the French l'oeuf for egg, to represent a zero. Or some say it is from the Dutch lof, meaning honour. "Deuce" to mean a score of forty-forty, is almost certainly just an anglicization of the French deux, for two, like in playing cards, or deux de jeu, meaning "two points from the game", to indicate that two clear points are needed to win the game. And "ace" to  mean an unreturnable (or at least unreturned) serve is probably also adopted from the ace in cards to mean unbeatable, although why the connection with cards is anyone's guess. As for "all" to indicate a tied score? No idea.
It is surprisingly difficult to pin down the origins of the strange terminology that we now take for granted in tennis scoring. Even the word "tennis" itself is of uncertain origin, although it probably comes from French and Anglo-Norman words like tenetz, tenez and tenes meaning "hold!" or "take!", which may have been called out before a serve, rather like "fore" in golf.
So, any wiser? Nah, thought not.