Well, it's hard to know all of the things you might be doing wrong from a couple of screenshots, but here's what I can glean from them (as well as general VGT advice):
-You definitely seem to be on the right track, for one thing. An Orc Monk with 75% both resistances can indeed wipe the floor with Horatio and the tower in general. I feel like your damage ought to be higher, though... did you desecrate Taurog's altar or something? (or maybe I just don't play the Monk enough.) In general, high damage and high resistances are *the* best attributes to have for the tower, and all characters are aiming for them.
-First thing I noticed is that there are blood pools all over the place, which tells me you aren't using Dracul. Now, it's possible that Dracul's altar was going to spawn last in the layout you rolled for this character, which is down to luck, but pretty much every character is going to want to convert to Dracul and grab Blood Shield + 3-4 levels of Blood Tithe in this dungeon, usually finishing it as a follower of Dracul. Blood hunger is also great, but if your character's resists are maxed out (especially as a Monk) it's not worth the max-resist cost. Do note that, as a Monk, you should usually have blackspace left over by the time you get to Horatio, so this may not be the main issue with your play, but it's worth mentioning.
-Blackspace conservation in this dungeon is probably more important than in any other dungeon, because it's fairly limited for the amount of strong monsters you have to fight. This is doubly true for the Monk, obviously. I don't know if you're already doing this, but you should absolutely avoid exploring the outer layer of tiles of the main floor until every other tile has been explored (unless it's to pick up something or check out a shop). That way, you minimize the amount of tiles you uncover without a chance of finding something useful underneath. Similarly, keep in mind how many monsters you've already uncovered on each floor; if you've uncovered every monster + the altar, consider whether you might uncover tiles on the main floor that could lead to popcorn monsters, pickups, etc. If you need to, count exactly how many tiles you'll need to regenerate to tank the next hit from a monster, so that you're not wasting and not accidentally overhealing the monster. Smart use of mid-fight level ups is a given, though sometimes you just want the level up to trigger at the end of a tough fight so you don't have to spend blackspace to regenerate from it (sorry if this is obvious to you, but VGT is the dungeon that really taught me to do those things methodically).
-How effectively are you dealing with the curses and special monsters? Each character class has certain special monsters and certain floor curses that are especially difficult to deal with (for the Monk, obviously, there's the cursed floor and cursed dragon, as well as the fully-explored floor and the poison-manaburn floor, etc.) It's important to be ready to deal with those threats in advance. As a Monk, carefully managing your popcorn so you have ways to remove Curse stacks is crucial. Preparing a Fortitude Tonic and a Burn Salve (or at least the Apothecary prep from Bezar) is also very important. Figure out when to use those based on whether you've already fought the Illusion and the Golden Statue, and try to align your use of the Burn Salve with an Earthmother desecration.
-What's your strategy involving Tikki Tooki? Four levels of Learning is very impressive, but VGT is probably one of the dungeons where such a feat matters least (not that it's useless, but I imagine that a *lot* of resources go into that that could be directed elsewhere). Personally as a Monk I would've only taken dodging and a shot or two of poison then converted out, but you don't need those to beat the dungeon. Personally as a Monk I prefer to prepare Taurog and get both the Sword and the Helmet for damage (no need for the armour, your starting resists with Dragon Shield are already very high). Taurog's damage boosts are exceedingly helpful for the Monk, and the extra magic resistances are basically necessary. From there, you're likely to want Body Pact and/or Blood Shield to boost the magic resistances further. Many people prepare Patches on most characters for the chance of getting further resistance boosts, though as a Monk I find the Smuggler's Den to be both more useful and less likely to screw you over. Remember that the earlier you get both your resistances and damage high, the better you can save resources for the higher floors and Horatio.
-Minor point: Do you have any Veto Slots unlocked? Filling those with items you don't need (especially items that spawn often) increases the chance of getting items you do need. Hero's Helm, for instance, is rather expensive for what it does (as far as I remember, I've had it vetoed for a while). That Viper Ward is super useful for the Monk, so the more likely you are to get it, the better your chances are. Also, speaking of inventory, the best glyphs in this dungeon are Halpmeh, Getindare (though a bit less so for the Monk) and Bysseps. As inventory space gets very limited, definitely formulate a plan before you pick up certain useful-but-not-essential items, lest you find yourself stuck having to convert something you don't want to convert.
-Finally, the classes which have the easiest time with this dungeon, in my experience, include the Rogue, the Vampire, the Paladin (Dracul) and the Monk. The Wizard was also quite good. Most of the classes should be Humans, since the Attack% bonus really makes a difference when you spend so much time at lvl10. Monks can also be Orcs (my personal preference) and Rogues can be Dwarves (usually prepping Taurog) or Orc/Human (usually prepping Glowing Guardian). My personal most reliable strat for the dungeon is the Glowing Guardian Orc Rogue, though you should play with what you're most comfortable.
That's all I've got for now. Feel free to ask more specific questions, or wait for other players who have more experience with the dungeon than I do!