The May meeting is when your Council should be deciding who is Chair, Vice Chair and which councillors belong to which committees. This should be done every year in May anyway, but particularly in an election year. Strictly speaking, he can't just nominate himself to be chair either; he should propose and have someone second - but this should be the case with any motion (although it's not often followed through on).
You'll need to watch what happens very closely if you have the situation you're describing and enforce the rules if the clerk is willing to let things slide/work with one person. It's a pain in the arse, but I would spend the next two weeks doing an awful lot of reading and understanding if you're new to the game. Standing Orders, Financial Regulations, terms of reference for any committees you have (all of which should be on your PC website and certainly available from your clerk) and try to get hold of some of the more "day-to-day" procedural Legal Topic Notes from NALC. These offer legal understandings about rules and procedures on a given topic. LTN 5E is a good one for procedures in meetings. You might get lucky and find one online...
The only way you'll be able to force the clerk to pay attention is if you prove to them you know the rules and you apply them correctly because for a dodgy clerk, having a bunch of ignorant councillors means they can get away with... let's say "making things easier for themselves"(!)
Also, try to get your papers signed ASAP. The sooner you sign them, the sooner you can start acting as a councillor and you won't get stupid excuses like "I couldn't send you the agenda because you wasn't a councillor at the time" etc