Also, as far as the contract goes, this seems a little fishy (moreso than the other stuff, at least):
I. RIGHTS AND TERM
Artist grants to Retailer exclusive world-wide rights to sell all painted canvases created by Artist and sold for as long as this contract is in force. Retailers rights shall include all direct and indirect sales of painted canvases at any location, domestic or international. This exclusive contract is intended to include all canvas sales of the Artist, whether direct to the public or to a third party or agent for later retail sale. Contract shall be in force from the date of execution and for five years thereafter. Contract will be renewed automatically unless discontinued by the method detailed below. The sales price of each canvas shall be set by Artist, however, Retailer shall have the right to set a minimum price for each canvas.
So I see that thing about discontinuing, and try to keep an eye out for it while I read the rest of the thing, and all I can find is:
VII. TERMINATION
Notwithstanding the terms set out above, contract may not be terminated.
XIII. BANKRUPTCY AND INSOLVENCY
If a petition in bankruptcy shall be filed by or against the Retailer, or if it shall be judged insolvent by any court, or if a Trustee or a Receiver of any property of the Retailer shall be appointed in any suit or proceeding by or against the Retailer, or if the Retailer shall make an assignment for the benefit of creditors or shall take the benefit of any bankruptcy or insolvency Act, or if the Retailer shall liquidate its business for any cause whatsoever, this agreement shall terminate automatically without notice, and such termination shall be effective as of date of the filing of such petition, adjudication, appointment, assignment or declaration or commencement of reorganization or liquidation proceedings, and all rights granted hereunder shall thereupon revert to the Artist.
So according to section I, you can only terminate the contract after five years by the "method detailed below". Unfortunately, there is no "method listed below" (unless I missed it), so that contract will automatically renew itself every five years until the retailer (or one of his heirs) goes bankrupt.
So, at the very least, the contract could be considered incomplete or misleading. Of course, the fact that you did still sign it will probably work against you.
If you really prefer painting on boards and stuff, you may want to just stick with that. The contract you signed specifically refers to painted canvases, so this person has no claim on any piece of work you do that isn't on a canvas.