A:
This question about proxies is not covered in RONR, and may vary from state to state.
You may want to consult an attorney licensed in your state for a definitive answer.
In my opinion, a member is represented by a proxy in his absence.
One cannot be both present and absent at the same time at the same place.
So, no, a member cannot "be present by proxy."
Even if every member were present and voted in favor of allowing proxies, the vote would be null and void because it would be in violation of your bylaws.
See RONR p. 12.
If proxy voting is to be allowed, it must be stated in your bylaws.
See RONR p. 415.
Therefore, if your organization wishes to allow voting by proxy, its bylaws must be amended by following the proper procedure for amendment.