I'd recommend a 2/4 or 2/3 with shadow/intimidate. A 4/4 for CMC4 with just an ETB is just a doublebear on the board which is a big butt but can get chump'd for days. I would expect the value of this card to be more in the triggered effect but, considering its spirit effect, maybe hexproof or some keyword would make it feel better.

Honestly I would love for this to be a sacrifice card. 1WG, Wolf Spirit, 1/3. Sacrifice Cian's Messenger, Flicker/Blink/Hexproof/Indestruct wolves and werewolves you control until EoT (or something), then draw a card.

I'm curious as to the ideology of the life gain and card draw. While the life gain is very fitting for the color wedge your playing in, the card draw does not aptly fit. So giving both feels very out of spectrum. A scry effect based on power/toughness/number of wolves or rummage for a creature/land would be much more in-line with the green roots.

Seeing this thing get Rite of Replication'd in its current text would be nutz.

Neither shadow nor intimidate are fitting keywords for this really, not to mention that shadow was very restricted and I don't want to bring such rare keywords back for a one-time use. Also it is more of a value card than a beater really, at least on it's own. Also werewolves have quite some ways to pump attackers, so a creature with shadow (or something alike) that is hard to block would be over the top I think.
For the sacrifice concept, that would be an entirely different card too and a one time draw is also not that bad if you can get something like Beast Whisperer for one mana more and protection stuff already exists plenty in those colors so i don't really see the need to make a new card for this either in all honesty. Also, idk why, but it feels so much like a cantrip that way to me.

Green has various cards that let you draw a card whenever another creature (usually non-token) enters the battlefield, so this is very on color for green where the lifegain naturally represents white. Beast Whisperer, Soul Of Harvest and Guardian Project to name a few. I added the draw for transformations for a bit more tribal synergies and feelings.

I mean so many cards 'would be nutz' if you cast rite of replication on them (which isn't in the colors you would want to go with in a werewolf/wolf deck). And it wouldn't win you the game right there either. Yes it would be good, but if I can cast a kicked Rite of Replication already I would actually want it to be more game winning.