Yeah I had similar thoughts about
Gravity Well. It's significantly easier for me to Zenith or Calling a
Hornet Queen or
Tornado Elemental anyway, or if it's an alpha strike Rotation for
Glacial Chasm so it's always seemed a bit superfluous.
Lifecrafter's Bestiary - I cant help but think there's better suited stuff out there. The scry is cute, but digging one deep isn't amazing. If the draw isn't critical I feel like
Abundance would suit better. I was going to suggest
Mirri's Guile but you mentioned money so that's out as is
Sylvan Library. I just feel like
Abundance will dig you further towards what you need right now, plus the replacement effect for draw comes in handy from time to time, in that it makes it significantly harder to
Stroke of Genius you out of the game. Just a suggestion, if the pokedex works fine stick with it.
Temur Sabertooth is a bit of a build around card. If you're not abusing ETB triggers it becomes a lot less valuable. Not worthless as indestructible is still decent, but less of an all around utility piece. The Planar rocks I totally get btw, with your mana doubling effects you are golden for getting use from these. And with scant ways to get artifacts/enchantments/non permanent spells etc in mono green, you use what you have. And yeah I definitely get the
Tooth and Nail sentiment. I don't necessarily agree at all levels of the format, I think there's far more oppressive stuff out there (craterhoof itself is top of the pile in green to my mind) but it's a fair point nonetheless. Everyone has their line in the sand and I get that.
With regards to walkers, green is pretty lucky. There's some really good value in things like
Garruk, Caller of Beasts,
Garruk, Primal Hunter,
Nissa, Vital Force, and
Freyalise, Llanowar's Fury. There's probably more but these seem the best value off the top of my head. I don't necessarily think you'd need to go for proliferate/
Doubling Season either. Firstly there's
Pir, Imaginative Rascal, but secondly, most of the good walkers in mono green are blessed in that they have value in more than just their ultimates. Freyalise gives you mana dorks and a free
Disenchant, Primal Hunter gives you half of
Shamanic Revelation which is awesome, and most of the Nissa iterations give you some degree of recursion, ramp or land untap. There's nothing wrong with using these to advantage and not going all in on hitting ultimates immediately. In fact, I prefer this in my superfriends builds - my Vial Smasher and Kraum is built this way and does quite well. I also think this is about the least obnoxious way to play superfriends, too. Seeing someone hit ultimates immediately is a bit demoralizing.
All that being said, because they are kind of set and forget and don't require a large mana investment, there's a fair chance going down this route would be a big change in direction, in that there'd be less point in producing the obscene amounts of mana your deck probably currently does. What's the point in floating it if you don't need it right? I'm definitely not saying you should change tack, the deck looks strong. Just saying superfriends is totally possible and could even be fun.