70,000 records isn't all that many really. Speed issues can also be network related, so if the performance of other applications is also slow, then that may mean that there's not much you can do. Obviously there isn't anything you can do about indexes in the source data, but if you don't need every source field in the form, don't base the form on a table. The search form link may help, but there is another possibility if performance remains slow regardless of filtering records for your form. That would be to load a copy of the data locally if it's not overly volatile. I did this once for a complex situation and speed increase was dramatic. Windows Task Scheduler ran updates on the local data at night, which was only a matter of expediency. If that failed, a manual update only took 2 or 3 minutes and we were good for the rest of the day.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.