As I read through this, two issues come to mind. One of them is technical. One is not.
Technical first:
The database grows because Access creates a temporary structure when you open a query. This structure records something (we don't always know exactly what) about the records that will be in the recordset that results from the query. Updates also make new copies of records that will eventually replace the records being updated. Because of the way Windows uses virtual memory, these structures often end up as part of the Access file. Rapid growth of the file merely means it is active.
You can counteract some of that growth using the strategy of splitting the DB into a front end (FE) and back end (BE), then distributing copies of the FE to individual users. At least some of those temporary structures are created in the FE so that is an immediate reduction in what we call "bloat." If you then use one of those strategies that transparently replaces the FE every time the user prepares to launch the FE, you drop the "local bloat." Then you only have to worry about BE bloat, but that should be reduced to issues in updating.
You also mention that you have heard that a split BE is harder to update. If you mean "via UPDATE queries" then no, that is not correct. If you mean "by changing table structure" then you are correct, but this has to be considered a "cost of doing business."
If you have to modify a BE, it will be to update a data layout because there will be no forms, reports, macros, queries, or code modules to update in the BE. The only thing that should be in the BE would be tables, and would would hope that that your table structures are more stable than the parts in the FE. And if you did the split and used the dynamic distribution method, that update becomes automatic. In this case, you set aside a period of some number of hours once per week, once per two weeks, or whatever you can manage. Update and maintain the BE during that time, including making backups. Again, that is a cost of doing business.
The other side of this question is "charging the company." This gets into contract law, which in turn gets into employment. With a couple of hundred countries out there, I have no clue as to what laws apply to your situation. However, as a general principle, if you are a salaried or hourly employee of the company, what you do for business projects is the property of the company immediately. If you are NOT an employee but rather work under a contract, see the terms of the contract, but most companies write that so that they own work done for hire. The third case is if you are a contracted consultant, and again, check the contract. However, only consultants or contractors with highly limited contracts have any hope of owning anything for which it would be possible to charge for software services.
