Hi,

Thanks for your questions.

It sounds like you've been consulting research-based sites for information, so you may have already seen the University of Minnesota Extension page about white grubs in turf grass. Here's what the page says about insecticides, including BT.

--- Preventive insecticide treatments should be applied from late May to early August. The insecticide must be watered in with irrigation or rainfall to be effective (0.5-inch minimum). Applications after mid-August and in the spring time, when grubs are fully grown, are not effective. Insecticides available to homeowners for white grub prevention include Imidacloprid (Merit, etc.); Chlorantraniliprole (Grub-Ex); and Bacillus thuringiensis galleriae (grubGONE). In August - September apply a fast-acting, short-lived, curative insecticide to reduce the number of white grubs can be applies. Curative insecticides are not as good as preventive insecticides at reducing the number of grubs. Insecticide treatments after early October are not effective and are not recommended. Unfortunately, raccoons and skunks are much better at locating grub populations than we are and the first hint of a grub problem in your turf is likely to be that your lawn was "plowed" by varmints overnight. Insecticides for curative grub control include Trichlorfon (Dylox, Bayer Advanced 24-Hour Grub Control) and Carbaryl (Sevin, etc.). One-half inch of irrigation immediately after insecticide application is essential for good results and to promote recovery of damaged turf. If you choose to apply insecticides, read and carefully follow directions. ---

Incorporating white clover into turf has the advantage of providing food for pollinators and fixing nitrogen in the soil. As you wrote, it's unclear what impact incorporating white clover (not a preferred food source for white grubs) might have on the population of white grubs.

Keeping turf healthy and resilient by encouraging development of deeper roots through strategic watering is probably the most effective cultural control. 

Good luck!

The May 15 UMN Turf Grass Newsletter has an article about white grub management that may be more useful to you.