中 sets the boundaries of something, and contrasts the inside from the outside. So when you’re talking about time, and when you set the boundary as the whole year, including everything inside, you are talking about ‘year round’.
I got nothing for the rendaku.
I was a little doubtful about this at first, but I’ll be… It even has a separate entry on Jisho. Nice one! 
And if you mistake it for きんだま (which according to my keyboard is a correct spelling, but whatever), you have to put up with it for even longer. My mnemonic for that is, if you touch your きんたま to anything, you will contaminate it.
I’ve had that problem too! I finally figured out that I think of it as the same as “middle kingdom” for China, that sense of being in the middle, central, surrounded, which reminds me of “year round” rather than “within the year”. Best of luck with it, though.
oh my-- yeah that would work!!
部室 (clubroom). Because it looks like 部屋 (room). It’s in Master now, but it always comes back… my brain gets excited and types quickly because it always thinks “Easy! Room!” Nope… I hate it
Oh, and then there’s 大きい, 大した, and 大きさ. All introduced on the same level as well, so they’ll come back to confuse you at the same times.
That one in particular, now I can’t miss it because it’s made me so mad so many times. I immediately go OH THAT F’ING HARD ONE, THE IMPOSSIBLE TO REMEMBER ONE SON OF A… [gets it right immediately]
So I guess SRS does work, eventually. No promises to have all the hair you started with, though.
For all the complaints about jin/nin being arbitrary and difficult, I’ve never had too much problem with those. Tai/dai though, grrrr…
Yeah, I make up custom mnemonics just for those.
大切: What item of clothes is the most important? Obviously the tie. Having shirts and pants and stuff is nice, but you need a tie to make a good impression.
大学: College is known for being painful, so you could call going to college the “ die -study”
大気: You use your superpowers to change the atmosphere, so a tie made out of clouds forms around your neck.
大作: After your epic play is performed, you step out on the stage for praise. However, the first thing you hear is someone shouting ‘Your tie sucks !’ Feel the shock at how rude this heckler is. Feel astonished that they didn’t pay attention to your play.
大会: It’s a tie convention, followed by a tie tournament. How nice does your tie look? How well does it match your suit? How fast can you tie it, and with how little complexity of the knot? This is what you must improve in yourself, to win the tie tournament.
大体: Meaning-The General got to become General generally because he is imposing, he has a BIG BODY. Reading: The General runs up to an enemy, and shouts in his face: ”だい”, and then たいs the enemy in knots.
部屋 is a much more common word, so every time I see 部室 I do a double take and have to look again to make sure I read it right. 
Grammar helps with those. 大きい is an い-adjective, so it’s used to modify nouns. To change an い-adjective to a noun, you replace い with さ. Hence 大きさ is a noun. You can think of it as going from “big” to “bigness”, but nobody says “bigness” so it’s translated as “size” instead.
大した is a pre-noun adjectival. That basically means it can modify nouns like an い-adjective, but can’t be conjugated or put at the end of a sentence. You’ll still have to memorize the exact meaning, but hopefully knowing that it’s used to modify nouns helps you narrow it down.
yeah i still mess this up tbh
人 is a quantum mechanical kanji that exists as a superposition of several eigenstates - じん and にん - not collapsing to either pronunciation until you hit enter. and get it wrong. every single time.
oh you think it’s にん this time? it’s not when you hit enter. the word comes up again the next day? try to be clever, type じん. nope, the universe wants you to suffer, it’s back to にん again…
I like these ones. I know ookii and ookisa no problem
But then I always think ‘oo sh!t a’ with the other. That’s how I remember it though. It’s great to have a big poop!
<don’t know if we can swear on here. but it is taishita!>
I actually teach kids, and a few months ago I was typing (we’re all online distance learning) in math about how the ‘…numbers shift along the place value line…’ but I guess I was too fast and missed the f in shift. Just heard these little gasps from my 10 year olds…
What is… oh. OOOOOOOPPS!
That aside, you can notice that した is the past/completed form of する, and often enough, kanji that come before する (without any other accompanying kana) are usually read with their on’yomi. However, if you don’t know which is the on’yomi, then this might be confusing, so I don’t know if it helps.
Would it help if I said that 室 generally appears in compounds, and almost always indicates a room with a specific purpose (e.g. 寝室, しんしつ=bedroom, literally ‘sleeping room’)? That’s the reason it can never just be ‘room’. 室 on its own is ‘room’, yes, but it’s more typically ‘room with a specific purpose’.
For nin and jin, I try to associate it either with a ninja or genie. Ryourinin is a ninja with mad cooling skills. Henjin is a goofy genie… And such.
For tai and Dai, chuu and juu, chi and ji… I usually try to come up with some mnemonic on the spot. Brain usually makes it stick. Eventually 
Can’t remember that 通 is read つう. Keep answering つ.
Funny you should ask because it is one I struggled with too. I finally have in my brain. Now, it’s 作る (to make) the reading is つく pronounced skudu. I want to always use jukugo on this one. 
It’s not pronounced skudu, actually (except by Scooby-Doo). The “ru” sound in Japanese is not the same as the “ru” sound in English, but the closest transliteration is “tsukuru”.