Using broad match keywords is a sure way to get lots of irrelevant traffic and burn through your ad spend budget with very little value being generated. I suggest you use broad match keywords only as a limited method to discover search terms that may be relevant and incorporate those into your ad groups using exact match keywords.
Broad match keywords may prevent your “profit-generating” exact match keywords from triggering ad impressions, so you might want to create a separate “testing” campaign for those broad match keywords. That way you can manage the ad spend budget separate from your profit-generating campaigns. Otherwise, irrelevant search terms could use up the bulk of your daily budget, preventing your profitable exact match keywords from being displayed at every opportunity.
Regarding your question about the number of keywords per ad group, there should not be a specific number that you want to include in a single ad group, as long it is at least one keyword that is fine.
The guiding principle is that every keyword, within the same ad group, should have the exact same meaning to searchers, and include nearly the exact same terms. This allows you to craft an ad text that matches the searchers’ intent in a very precise manner. The goal being to have the most compelling ad text for the search term. You can include every keyword that meets those criteria, it is typically a very small number per ad group.
This does not, in any way, limit the number of keywords that you can include in a campaign. Just create whatever number of ad groups, and ads, needed to accommodate your keyword list.