Air carrier Captain reported an unstable approach; initiating action for an RA; performing a missed approach for traffic on the runway and leveling off at an altitude below the MSA; all due to ATC handling.

Narrative

I was pilot flying when we were handed off to ZZZ Approach. There was weather in area which added additional threats in which we briefed well ahead of time. They delayed our descent which keep us well above the normal descent. Approximately 7 miles out we were still well above normal descent and were cleared to the fix ZZZZZ just outside final and cleared for the approach. We were told by Tower to slow as practicable due to military aircraft in the area. We where give location of multiple jets who where circling east of Runway XX. We had them in sight when we received a RA to descend. We complied as I was hand flying and descending already. Shortly afterwards we were cleared to land on Runway XX. At approximately 200 feet from landing we spotted what appeared to be an aircraft on the runway (which we were never told of) Tower told us to go around and maintain 1000ft. We queried about the low level off and no sooner we spotted a jet directly above us approximately 500 ft flying in same direction and accelerating. We were given an immediate turn to the west and handed off to Departure. Upon the call to Departure we were told to climb to 2000ft immediately due to the 1600 MSA in the area. The Departure Controller didn't understand why we were given the 1000 ft level off from the Tower. We where vectored for a right downwind to land on Runway XX. Upon landing in ZZZ I requested a phone number to call Tower so I can express the potential safety risks we encountered. Luckily; the First Officer and I where able to trap these threats and eventually land the aircraft safely back to Runway XX. Cause: Multiple military aircraft and commercial traffic in same airspace at same time. Additionally; keeping us high and than asking us to reduce to slowest practical airspeed creates an unstable and unsafe condition