Treaty was just as valid as the ABM treaty we pulled out of under Bush 43. We are pulling out because the Russians have deployed intermediate nukes and Bush and Obama protested and did nothing in response.
If I were Trump I would bring up a Pershing like nuke being deployed in Poland and set it in motion and ask Putin if he wants to follow the INF treaty or not.
I would just assume that the Russians would not follow any treaty, and any pretended compliance would only last until the next Democrat administration, so we might as well scrap the treaty, do a bunch of testing, and build and deploy a bunch more nukes.