TBH, it sounds like you're going to have a rough time because you're giving yourself restrictions that your opponents don't have. Proliferate infect is, by design, very hard to interact with, and ramp can be a pretty "solitaire" deck archetype, your opponent either has a board wipe on the right turn or they don't and die.
You could play counterspells, or discard, or stax, or land destruction, or just a ton of removal, but if your goal is to play a non-combo (so your opponents can interact with it) non-control (so that your opponents can still play cards) deck that can fight an aggressive ramp deck and a value-engine proliferate and infect deck, you don't have a whole lot of options.
You could try to be more aggressive than they are, maybe? Not easy to pull off in EDH, but there are some pretty effective Voltron decks that can beat people to death quickly. It's definitely interactive since you're relying on dropping permanents and attacking with creatures, and it tends to punish decks that don't pack removal reasonably well if it's aggressive enough.