Celebrim
Legend
a) So far the low level magic is really not game imbalancing.
The problem with the trope is not so much that magic is imbalancing (5e is presumably well balanced magic) but that no NPCs in the setting seem to be aware that magic exists, has never before dealt with a magic user, and knows less about the abilities of magic users (something that in their world exists) than modern people know about the abilities of zombies and vampires. It might be one thing if they had misperceptions about wizards, but so often I see campaigns were the DM assumes both that there is a magic shop in town but that no one has ever seen or heard of a spell being used before for a nefarious purpose.
Not a fan of monks or--to be honest druids either.
Coming clean, I removed barbarians, paladins, monks, druids, and rangers from my house rules. I replaced them with alternatives (fanatics, champions, shamans, and hunters), but the classes themselves I felt carried too much baggage and had to go. The alternatives are at least clean of unnecessary setting assumptions.
...but falling damage is BS.
I waffled back and forth between the exponentially increasing damage concept (which I used in 1e) and a more complex 'Russian Roulette' rule that kept falling potentially dangerous, but meant that on the average falling was no more dangerous than in traditional D&D. I went with the complex rule mainly for game balance reasons. The basic idea here is that the average damage is about 3.5/10' fallen, but it's not on a normal curve and the upper end is quite open ended. One way you could do that is with exploding d6's, but I don't like exploding dice particularly so I have a system where in a nut shell you roll d20's for fall damage but you divide the resulting damage by 1d6. If you throw that '1' for the divisor dice, falling is pretty darn lethal, averaging over 10 damage per 10' fallen. I don't in general feel the need for making falling more harsh than that as a matter of verisimilitude. So long as the range of possibilities includes the range of real world possibilities, I don't worry too much about the odds.
In general, this is explained/handwaved by magic as physics. You don't fall in my game because of gravity. Gravity per se doesn't exist. You fall because Earth spirits pull you to the ground. Likewise, one thing a physicist in the game world would observe is that kinetic energy would be linear with velocity, rather than exponentially increase with velocity - Gravesande's experiment would yield a completely different result. So there is no need for perfect consistency with real experience, because you are in a completely different world that only superficially resembles this world in casual observation (to the same extent that this world could be casually mistaken for a world that worked according to pre-modern understanding of physics).