Business solicitor - Advertiser Terms and Dispute Resolution

Have a german client (advertiser) that has bought adverts in 2022. Used some, not used others. We are UK company. Order was placed online via our website and terms are contract is UK. Digitally signed by reading terms and confirmation. He published 28 adverts. 27 of them breached terms and he was informed of the adverts needing changes to comply, but not specifically, just refer to Advertiser Terms. He breached contract and was informed of breaches which invoked a penalty clause in our advertiser terms for each 27 adverts. 27 penalties added to his online wallet as negative balance. After informing him of breach and actions he wants to cancel, keep adverts he paid for and get a full refund and mentions compensation. We have prepared an overview, his request and our resolution. Need help to check our proposal of resolution and retain rights if not accepted. We need to make sure our terms are solid and make better if need be based on this test case. Need to check distance selling also if it applies to German business to business.