You can grow it as large as you want, and it generates treasure tokens when it dies
Its controller does get some card draw-based compensation though, in the form of one of the junk tokens, which look to feature heavily in this deck, and are much more useful than they sound
A deck focused on aggressive strategies and utilizing poison counters would benefit from including Spinebiter, as its Infect ability can quickly weaken opponents and potentially lead to a win through poison counters
I am religiously following his tutorials and wonderful art videos
Malice in Underground provides searching and power boosts for Malice Link Monsters, making it a perfect Field Spell choice
Yes, the activated ability lets you sneak your creatures onto the battlefield, while the triggered ability improves your scrying