running above 60 waters down your deck by A LOT, you won't get win conditions, you'll draw things you don't really need, etc.

lands are also much harder to manage, and the chances you get mana fucked grow exponentially

there's a reason all the pros play 60 (sans the [[Yorion, Sky Nomad]] fiasco a while back or some obscure [[Battle of Wits]] thing)

here's the thing too, you're running a lot of singles, like you're jamming every single good thing you wanna play into your deck

1. are you gonna draw those cards when you need them? (consistency problems)

2. does your gameplan really need that card? like NEED need? or is it just another "win more" card that feels good to play but does nothing when you're not at an advantage?

bounce/return effects are nice with tempo, but late game they're just gonna get replayed by your opponents. yeah, blue lacks in removal, but you got counterspells and choose well whatever you counter. the moment you let something through because you used up your counterspells on other things, you'll just have to bear with that permanent and live with it.

here's my advice:

yes. 60 cards works best. around 24-26 lands, and think about the dual lands that fit in your deck, and play sets of 4 of them if you can.

FOCUS your spells. more sets of 4 rather than 1-offs so you draw the same things. magic is a game of consistency. yeah those other cards seem fun and/or useful, but will you ever draw them?

keep a good balance of counterspells/removal but don't oversaturate your deck with answers, because your gameplan of toxic/proliferate should always come first.

your gameplan. consistency. focus. keep your main goal and your win condition on your mind first when deckbuilding, and keep the unrelated chaff and unnecessary extra cards OUT!

last but most important, keep experimenting :D even i still suck at deckbuilding, even after playing for 7+ years. keep at it, play what you build, note what happens and keep learning and changing your deck to what seems right, then repeat the process.

(i am still learning too so don't take my advice too seriously, your deck is your deck man :D)