Is the revision considered legally valid after the husband has two witnesses attest to his desire to revise his wife, given the rejection of the wife's guardian and his demand for financial and gold compensation, knowing that the wife is pregnant and wishes to return to her husband, and that the guardian prevents communication between the spouses?

If this was the first or second repudiation (talaq), then your wife has returned to your marital bond (ismah) by your taking her back before the expiration of her waiting period (iddah), especially if you had witnesses to this return. Her guardian has no right to prevent her from returning to you or to demand money in exchange for her return. As for the gold that your wife gave you, if it was a loan or something lent for use (ariya), then it must be returned to her. However, as long as she has given you time to return it, her guardian has no right to demand it from you. It is advisable to seek mediation through some people of religion and integrity, otherwise, resort to the Sharia court.