僕らはお互いを電話すれば、お互いをわかりますかな?

• 僕らは is not necessary because it's safely inferred from the context.
• Unlike call, 電話する is not transitive. The particle you need here is に. Or you can just use お互い without any particle because it also works as an adverb.
• ～ますかな is a very pompous way of asking a question. I hear this only in fiction, typically from noble people and stereotyped elder gentlemen.
• Neutrally saying ～ますか is not a good way to ask a question like this anyway, because you are expecting a positive response. (i.e., You want to say "we do ... don't we?" or "Don't we ...", not simply "Do we ...")
• 分かる is rarely used transitively. Use ～が分かる isntead.
• Try using ～あう here. If you can use this the second お互い is redundant.
• "At all" in a positive sentence can be translated as とにかく, ともかく, 何にせよ, etc.

Fixed version:

• お互いに電話すれば、お互いが分かるのではないでしょうか。 (still slightly clumsy)

• 何にせよ、お互い電話すれば、わかりあえるのでは？
• 電話で話しあえば、ともかくわかりあえるんじゃない？ (casual)

僕らはお互いを電話すれば、お互いをわかりますかな?

• 僕らは is not necessary because it's safely inferred from the context.
• Unlike call, 電話する is not transitive. The particle you need here is に. Or you can just use お互い without any particle because it also works as an adverb.
• ～ますかな is a very pompous way of asking a question. I hear this only in fiction, typically from noble people and stereotyped elderly gentlemen.
• Neutrally saying ～ますか is not a good way to ask a question like this anyway, because you are expecting a positive response. (i.e., You want to say "we do ... don't we?" or "Don't we ...", not simply "Do we ...")
• 分かる is rarely used transitively. Use ～が分かる isntead.
• Try using ～あう here. If you can use this the second お互い is redundant.
• "At all" in a positive sentence can be translated as とにかく, ともかく, 何にせよ, etc.

Fixed version:

• 僕らはお互いに電話すれば、お互いが分かるのではないでしょうか。 (still a bit clumsy)

• お互いに電話すれば、とにかく分かり合えるのではないでしょうか。
• 何にせよ、お互い電話すれば、わかり合えるのでは？
• 電話で話しあえば、ともかくわかりあえるんじゃない？ (casual)