I have been using Airtable as a project management tool for my company and can confidently say it will meet your needs for items 1 and 3 with minimal effort. Airtable is capable of meeting your other three needs. However, it will take quite a bit more work. My only major concern is how fancy the Gantt needs to be for you. Airtable has a reasonably nice Gantt, but if you are tracking more than a hundred tasks it can be a bit difficult to make readable.
Airtable support is awesome and I’m sure they can help make sure you get where you need to! Just make sure you contact them at the outset and make it clear you need some help to get your company started here.
@PMOguru Glad to know that you got the answer you were seeking! If you would, please mark the comment from @Paul_Warren as the solution to your question. This helps others who may be searching with similar questions. Thanks!